ness to the pace of biological advance and its accessibility to the most perilous genocidal experimentation.

The U.N. has had a long history of abortive attempts to start discussions on the control of BW.

Now, the British delegation has introduced new initiatives for BW controls and, evidently with some reluctance, the U.S. State Department for the first time agreed to substantial technical studies. Time is running out, and too little is left to let BW remain merely another minor pawn whose disposition is incidental to other settlements.

[From the Washington Post, Aug. 31, 1968]

THE INFAMOUS BLACK DEATH MAY RETURN TO HAUNT US

(By Joshua Lederberg)

In mid-14th century, the Crimean seaport of Caffa (now called Feodosia) was an important fortified outpost of Genoese traders. For the previous 50 years, Genoa had been in intermittent conflict with Venice, and with factions of the Mongel Golden Horde. The famous Travels of Marco Polo were written while this Venetian adventurer was a prisoner-of-war in the hands of the Genoese.

In the year 1346, Caffa was again besieged by the Mongols. During this same time, a vast epidemic of bubonic plague had rapidly spread through the Mongol empire. In the words of Gabriel de Mussis, a contemporary chronicler, "The Tartars, fatigued by such a plague and pestifrous disease, stupefied and amazed, observing themselves dying without hope of health, ordered cadavers placed on their catapults and thrown into the city of Caffa, so that by means of these intolerable passengers the defenders died widely."

After this bacteriological attack, the survivors abandoned the city and returned to Genoa as best they could. By 1348, the Black Death had devastated Europe. Dr. V. J. Derbes of Tulane Medical School, writing in the Journal of the American Medical Association (April 4, 1966), pointed out that the plague would undoubtedly have reached Europe by trade routes, regardless of this incident. Nevertheless, what is known of the spread of the Black Death, starting from the Italian seaports, is consistent with attaching it to the return of the Genoese ships from Caffa with a heavy cargo of infected rats and fleas.

Plague is still with us. It is usually associated with tropical, rat-infested environments, and indeed it was again killing a million people a year, mostly in India, at the time of World War I. Since World War II, vigorous rat-eradication programs have succeeded in holding plague deaths down to a few hundred. The disease has, however, gradually spread to native, wild rodents throughout the world, where it smolders, only to break out in an isolated case or small epidemic of "sylvatic" or forest-living plague. The deprivations of war, as in Vietnam, also foster new outbreaks of plagues.

As far as we know, these outbreaks are caused by the same bacillus that spread the Black Death. However, the organism does show considerable variation under laboratory conditions. An epidemic of the Black Death may have reflected the evolution of some especially virulent and contagious form of the bacillus. Fortunately, streptomycin and a few other antibiotics are remarkably effective. Nevertheless, human ingenuity is quite capable of wasting the good fortune of the human species. Mutant strains of the bacillus that are indifferent to antibiotic therapy are easily cultured.

The potential of plague for biological warfare (BW) is obvious in the light of the historic precedents. Any intelligent program of BW research, especially if its main mission were "defensive," would have to develop aggressive, drugresistant bacilli in order to evaluate them as a military threat. BW research must also be concerned with the factors that encourage the airborne spread of pneumonic plague.

The Black Death of 1346 probably could have been contained with the resources of modern medicine. When hostile bacilli have been augmented by human intelligence, however, any confidence that they can be contained is a delusion.

The disastrous course of present-day Soviet militarism makes it vastly harder to attempt a world settlement for the surveillance and control of BW agents. But BW can add nothing to the strategic power of nuclear-armed states. If in

nothing else, we should be able to find a common cause in protecting ourselves from a recurrence of pestilence. Or must we console ourselves with the recollection that the Black Death helped pave the way to the Rennaissance?

[From the Washington Post, Sept. 7, 1968]

MANKIND HAD A NEAR MISS FROM A MYSTERY PANDEMIC

(By Joshua Lederberg)

In the aftermath of the six-day war in the Middle East last summer, direct air transport from Uganda to Germany and Yugoslavia was disrupted. Shipments of "green monkeys" for use in preparing vaccines were diverted to London airport before transshipment.

In the process, a group of at least eight monkeys acquired a disease heretofore unknown to medical science. The disease remains unnamed but might be called Marburgvirus, for it infected at least 32 people and killed five of them in Marburg, Germany, and infected two in Frankfurt.

Twenty-seven of the infected cases were among laboratory workers who handled the monkeys or their organs. Five were secondary cases, nurses or doctors who attended the primary ones and were in direct contact with the patients' tissues or secretions. In a brief review in Nature magazine, Dr. C. E. GordonSmith, director of the British biological warfare research laboratory at Porton, also alludes to the transmission of Marburgvirus as a venereal disease, but this is perhaps conjectural.

There is, however, no doubt that Marburgvirus is extraordinarily contagious and rapidly lethal in a distressingly high proportion of cases. It is found in the blood, throat secretions and urine of infected animals and men and direct contact is the only known medium of transmission. What might have been an epidemic of world-shaking dimensions was contained by the sheer good luck that it did not spread to man at London airport but first appeared in the medically knowledgeable environment of the laboratory destinations.

The Porton laboratory was involved when the unusually contagious character of the new disease was first realized by the German physicians. As its director remarks, "The facilities for the study of infectious diseases are of a kind probably unmatched in Western Europe; there is a strict code of safety and specially designed apparatus to cope with hazardous operations. Elaborate precautions are taken to prevent the escape of infective material and a research section is devoted solely to the study of laboratory hazards."

Its scientists were then especially prepared for the further experimental study of the new disease. They soon showed that the Marburgvirus was quite distinct from any previously known disease agent and quite unresponsive to every antibiotic tried.

The virus is also under study in Johannesburg and in the United States Public Health Service researchers at the Communicable Disease Center at Chamblee, Ga., have confirmed that it is a new virus though possibly related to the vesicular stomatitis of cattle.

The origin of Marburgvirus is unknown. It may be indigenous to green monkeys in Africa; it may have been acquired by contact with other animals in whose company the monkeys were held during transshipment through London.

The threat of a major virus epidemic-a global pandemic-hangs over the head of the species at any time. We were lucky on this occasion, but it was a near miss. It could easily have established a very large focus of infection in countries like India or China or South Vietnam, and in our present knowledge of virology we would have been ill-equipped to stop it from dominating the earth, with a halfbillion casualties.

We have also seen the irony of the constructive role played by a BW laboratory in containing the virus. But we cannot blind ourselves to the knowledge that biological warfare now has one more potential weapon in its repertoire. Furthermore, a great deal of scientific ingenuity is dedicated to "improving” such agents, the most suicidal of human enterprises today.

Marburgvirus is but one example of the evils of nature that are our real enemies in the living world. It is very unlikely to discriminate between Democrat or Communist or Maoist. And as human society is now organized, our encounters with such threats will not for long be just near misses.

[From the Oak Ridger, Oak Ridge, Tenn., Sept. 9, 1968]

Science and Man

HAILING ORNL EXAMPLE OF "GENETIC ENGINEERING"

(By Joshua Lederberg)

Recent advances in fundamental biochemistry have generated much speculation about genetic engineering, the calculated modification or design of an organism based on new knowledge of the genetic code. Now the first factual example to illustrate such an effort has been reported.

(The report in Nature magazine, by Drs. Stanfield Rogers and Peter Pfuderer, of Oak Ridge National Laboratory, also indicates the broadening functions of these laboratories, for the research was sponsored jointly by the Atomic Energy Commission and by the National Cancer Institute.)

In higher organisms, the genetic code is embodied in the DNA of the chromosomes of each cell. This is then translated into multiple copies of RNA "messenger" molecules and these in turn regulate the formation of the various proteins that make up the cell.

Some simple viruses, like the tobacco mosaic virus, have a simplier life cycle that bypasses the DNA. Instead, their RNA functions both as the hereditary material, being able to replicate as such, and as its own messenger. The tobacco mosaic virus, a disease of tobacco plants, has been much used for basic studies of virus biochemistry.

Previous studies pioneered by Dr. Marshall Nirenberg had established that the triplet in messenger RNA that reads “A-A-A-" (A standing for adenine) is translated into the amino acid protein chain. Rogers and Pfuderer used a specific enzyme to add a chain of about 18 A's to the end of the natural tobacco mosaic virus molecule. After purifying the product, they then used the modified complex to infect tobacco plants. If the dangling chain of AAA-triplets was translated according to modern theory, they reasoned, they should find new substances in the infected leaves, namely strings of up to six lysines.

This is precisely what they report.

The most important point that remains to be investigated is how the modified complex functions as a virus-that is, whether it replicates itself according to expectation. This information should be available very soon.

The result has mainly theoretical interest, by corroborating contemporary speculations about ways in which modified viruses-and, by implication, genes of higher organisms-can be artificially designed. We can expect to hear soon of methods of grafting two preexisting sequences together, so that tobacco mosaic virus could be extended with a more meaningful message than one for monotonous lysine strings. This could then lead, for example, to the production of virusinfected plants of precious and rare products like human growth hormone. Even monotonous sequences may have great economic significance. The AAA modification theoretically should exaggerate the amount of lysine manufactured by the infected plant. Lysine is one of the essential amino acids and many cases of malnutrition stem from a deficiency of lysine in the locally available food crops. We can readily visualize the engineering of tempered plant viruses that would augment the value of the protein produced by conventional crops.

The extension of this approach to animal viruses, furthermore, is one of the most promising approaches to a fundamental attack on genetic defects in man: the missing genes might be reintroduced into afflicted children by vaccinating them with specially engineered viruses.

There is, as always, another side to the coin. The lead editorial in the same issue of Nature remarks: "It is hard to decide why discussion of chemical and biological warfare has become so fashionable." But the obvious application of this new science to military progress in anti-human, viral weapons certainly adds new substance to our anxieties about biological warfare.

[From Book World, June 15, 1969]

ONE-THIRD OF EUROPE DEAD OF THE PLAGUE

(By Joshua Lederberg)

The plague has always slumbered here and there around the world. About the year 1340, it flared up in Central Asia near Lake Issyk Kul, to the east of Tashkent. Its ravages in Asia and India are uncounted. By 1346 it had reached the Crimea, a scene of brush-fire conflicts between the Genoese and Tartar empires. With an intuitive sophistication in bacteriological warfare, the Tartars infected the Genoese fort by catapulting their own corpses over its walls. The stricken Genoese fled back to Italy, carrying the plague with them and igniting an epidemic, known to history as the Black Death, that spread rapidly across Europe. During the next two-and-a-half years it is estimated that about one-third of Europe's population was killed by it. But we do not have accurate statistics, and other guesses vary from 20 to 60 per cent, which seems a reasonable range for the plague's impact on different communities. The survivors were beset by repeated but much milder outbreaks for the next sixty years.

In this excellent book, Philip Ziegler suggests that Europe had been weakened by several decades of economic and agricultural decline, but we have very little scientific information to explain the ferocity of the epidemic. Most specialists believe that the present-day plague bacillus would be quite capable of a similar recrudescence except for the availability of antibiotics and pesticides to control rat fleas, if not the rats themselves, both of which maintain the potential contagion.

Fourteenth-century Europe only dimly understood the role of contagion, and was told by its leaders that the plague was above all a visitation of a vengeful God for vaguely specified sins. In Central Europe the Jews were persecuted as scapegoats, according to long-established custom, but the persecutors discovered no immunity to plague by that route.

One historical side effect of the Black Death in Scandinavia may have been a weakening of support for the dying colonies of Norsemen in Greenland. This foothold collapsed before the rediscovery of the New World by a Genoese in 1492— and the fact that we celebrate Columbus Day is at least one historical consequence.

Ziegler tells the story with ample but not stifling documentation and with an engaging balance of detached statement and illustration. The statistical arguments about the mortality percentages are a necessary building stone and, happily, are assembled in one chapter. With equal discretion, Ziegler has written another chapter devoted to a fictional synthesis of the experience of a composite village in England. Though the primary data are sparse and Ziegler takes proper pains to point this out, he builds a most credible, restrained account.

His larger view brings out few conclusions that will surprise anyone who has read shorter accounts of the Black Death (like William L. Langer's in Scientific American, February, 1964) or chapters in history texts and encyclopedias.

The surprising thing about the Black Death is that it was assimilated into the historical life of the period without working any extraordinary change in its larger institutions. Despite the misery of individuals and families, most communities survived; government rarely broke down; inheritance taxes were duti fully collected on the suddenly increased numbers of estates; there were few direct challenges to authority or shifts in centers of power. One can speculate about the role of the Black Death in accelerating the breakdown of feudalism, but it is hard to substantiate an influence commensurate with the mortality figures. The Black Death was an unprecedented source of private bereavement, but it had minimal social impact, perhaps because it visited rich and poor alike, with little discrimination. Ziegler points out that the loss of teachers and clergy may have sped up the vernacularization of education and of the liturgy. We might also guess that it inspired some skepticism about faith in the power and truth of the Church, but this assumes a degree of rational intellectual commitment that is rarely evoked by real distress.

སྙན་

APPENDIX D

STATISTICAL ANALYSIS OF TERATOGENIC EFFECTS OF PESTICIDES

(By D. W. Gaylor, M. D. Hogan)

BIOMETRY BRANCH, NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES, SEPTEMBER 5, 1969

Introduction

This report contains a statistical analysis of the teratogen data collected by the Bionetics Research Laboratories of Litton Industries during the period 19651968 for the National Cancer Institute. The teratogen screening study contained 53 compounds chosen as representative of several chemical classes of pesticides and industrial compounds.

Four strains of mice were used: C57BL/6, AKR, C3H, and A/Ha. Most of the studies were performed with the C57BL/6 strain. A hybrid fetus resulting from mating a C57BL/6 female with an AKR male was used to study a few compounds.

Most compounds were administered subcutaneously in solutions of dimethylsulfoxide (DMSO). Water soluble compounds were administered in saline solutions. In some cases, the water soluble compounds were studied using both DMSO and saline. Compounds administered orally were suspended in a 50% solution of honey. A group of untreated controls were included as well as controls receiving only DMSO, saline, or honey. Females entered the study at the onset of their first pregnancy as indicated by a vaginal plug. Subcutaneous injections of 100 μl per mouse were made at the nape of the neck. Oral administration was by gastric intubation using a volume of 100 μl per mouse. Compounds were administered daily beginning on the 6th day of pregnancy and continuing through the 14th day (15th day for AKR mice). The mice were sacrificed on the 18th day (19th day for AKR mice) of gestation. Upon sacrifice, fetuses were examined for anomalies. Approximately two-thirds of the fetuses were then stored in Bouin's solution until they were necropsied. The remaining fetuses were treated with alizarin red stain. The numbers of resorption sites and dead fetuses were also

noted.

Because of the marked complexity of teratologic investigations in general and, in particular, because of the nature of the experimental design underlying the Bionetics study, several assumptions had to be made in order to statistically analyze the data from this study.

All statistical analyses were performed on a per litter basis rather than a per fetus basis, since initial investigations indicated that the occurrences of anomalies among fetuses within litters were correlated. The large litter-to-litter variation may be a reflection of some maternal effect, an indication of the effective dose level of the compound actually reaching the fetuses, experimental variation, or, as is most likely, some combination of the three factors.

Another important consideration that should be noted is that while controls were run periodically throughout the duration of the study, no effort was made to match compounds and controls with respect to either route or dates of administration since no time trends were anticipated. While there were no statistically significant time trends within the various control groups in terms of the onset of fetal anomalies in the C57BL/6 mice, the incidence of fetal mortality was certainly time-dependent in this strain, with 1965 being characterized by a low incidence of pre-natal deaths. Furthermore, there was a period of approximately six months, extending from the latter part of 1965 into early 1966, during which no control animals were run. During this period a change in the substrain of C57BL/6 mice used in the study took place. Finally, among abnormal litters, e., litters containing at least one abnormal fetus, there was some suggestion that the distribution of abnormal fetuses per litter was stochastically larger in the DMSO controls than it was in the untreated controls. Thus, one cannot