August 22, 1S95] 



NA TURE 



93 



jyj 



RECENT STUDIES ON DIPHTHERIA. 



IT is an acknowledged fact that as regards diphtheria, 

 personal predisposition on the part of its victims 

 plays a most important part. 



We find this well illustrated by statistics which sho\v 

 that it is in early childhood that the majority of cases 

 occur, and the heaviest diphtheria death-rate is recorded. 

 Thus Feer in Basel found that the most susceptible 

 age to diphtheria lies between the years 2 and 5 

 and 5 and 10 ; but that whilst the mortality amongst 

 children attacked in the earlier period was 254 per cent., 

 in the later period, with piractically no diminution in the 

 number of cases, the diphtheria death-rate fell to 7'6 per 

 cent. After this period there is not only a great decline 

 in the number of cases of diphtheria, but also a marked 

 decrease in the percentage of deaths, suggesting that 

 with increasing age the human system is enabled gradu- 

 ally to develop means of protection from this terrible 

 disease. 



That some such protective power must also be possessed 

 to a large extent by children, follows from the fact that 

 with a disease practically endemic in some of our large 

 cities, so many children succeed in escaping from its 

 ravages, for it is impossible to conceive that all those 

 who ha\e remained unscathed ha\e ne\er beer, exposed 

 to infection from diphtheria. 



Thus Fliigge has worked out an interesting diphtheria- 

 table for the city of Breslau during the years 1886- 1890, 

 in which he not only confirms Peer's observations upon 

 the connection between age and the diphtheria death-rate, 

 but he also shows very clearly that e\en in the most 

 susceptible period of child-life, the number of cases of 

 diphtheria is relatively small when compared with the 

 number of children of the same age who are not attacked. 



In what does this protective power against diphtheria 

 infection possessed by many children and a large number 

 of adults consist ? This interesting and important ques- 

 tion Dr. Wassemiann has recently endeavoured to answer 

 by making a veiy extensive examination of the properties 

 possessed by the blood serum derived from patients not 

 suffering from diphtheria, but admitted on other grounds 

 to the Berlin Institute for Infectious Diseases. Careful 

 inquiries were, moreover, in every case made as to the 

 patient's previous history as regards diphtheria, and only 

 those were included in the investigation who had never 

 had diphtheria. 



The serum which was obtained from these strangers to 

 diphtheria was in every case tested for its immunising or 

 protective power by inoculating it along with a recog- 

 nised lethal dose of diphtheria toxin into guinea-pigs, the 

 latter by itself having been proved capable of killing 

 these animals without exception in from 30 to 48 hours. 



The results obtained were extremely interesting. Out 

 of seventeen children varying in age from i^ to 11 years, 

 eleven yielded senmi with highly protective properties as 

 regards diphtheria, for all the animals treated with their 

 scrum and virulent diphtheria toxin experienced no ill- 

 efiects whatever. Two out of the seventeen children 

 yielded serum possessed of slightly protective power, it 

 being found capable of delaying the death of the infected 

 animals, whilst the serum derived from the four remain- 

 ing children had no protective properties whatever. 



.-\mongst the adults the number of those yielding an 

 anti-toxic serum was much greater, for out of thirty-four 

 individuals the serum of as many as twenty-eight was 

 found to be endowed with protective properties against 

 diphtheria infection ; and, as far as the investigation went, 

 it appeared that the possession of such serum, as well as 

 its strength or degree of efficiency, was more marked w ith 

 increasing age. 



That people who ha\e gone through the ordeal of 

 diphtheria possess such antitoxic serum in their system 

 has been shown by various investigators, but, so far as we 



NO. 1347, VOL. 55] 



know, Wassemiann is the first who has proved that anti- 

 diphtheritic serum may also be possessed by individuals 

 who have had no previous experience of diphtheria. 



This discovery serves to explain how virulent diphtheria 

 bacilli may be present in the throat of perfectly healthy 

 people, without producing any bad results at all. That 

 such may be the case has been proved by most careful 

 and trustworthy observers, and that their presence does not 

 engender diphtheria, we must now regard as probably due 

 to the possession of anti-diphtheritic serum by the indi- 

 \ idual who so unconsciously has harboured them. Such 

 may also be, and probably is, the explanation of the 

 harmless presence of virulent diphtheria bacilli in the 

 throats of patients convalescent from diphtheria long 

 after the disappearance of all the typical symptoms. 



It does not follow, however, that because at some 

 given time a particular individual has been found the 

 happy possessor of anti-toxic serum he may, therefore, 

 rashly assume that he is for ever after proof against 

 diphtheria infection. 



It must be remembered that such serum is possessed 

 in very different degrees of strength by different indi- 

 viduals, and may vary also, in one and the same individual, 

 in its protective character at different times. 



Research has show n that people possessing only feebly 

 antitoxic serum can contract diphtheria, but in the ma- 

 jority of such cases it is satisfactory to learn that the 

 symptoms are light, and the disease is mastered without 

 much difficulty. 



So far as our present knowledge goes, it would appear 

 reasonable to admit that although the possession or non- 

 possession of antitoxic serum of varying degrees of 

 strength may not be the only circumstance which regu- 

 lates the fluctuating personal disposition towards diph- 

 theria infection, that yet it may be regarded as an im- 

 portant factor, and Wassemiann considers principal 

 cause, in determining the apparent idiosyncracies of 

 diphtheria infection. What the mechanism may be 

 whereby this anti-toxic serum is produced in the system 

 is still a mystery ; that it should be possessed by infants 

 only eighteen months old, would incline to the belief that 

 it is natural or inborn, and not subject to later processes 

 of evolution. 



On the other hand, howe\er, we have the well-estab- 

 lished fact that the serum of animals which have a natural 

 or race immunity to a particular disease, is wholly devoid 

 of power to confer protection from this disease on other 

 classes of animals. 



This remarkable circumstance has been once more 

 very clearly demonstrated by Wassemiann in the case of 

 diphtheria, to which disease white rats are absolutely 

 immune. In order to test the character of white-rat- 

 serum as regards diphtheria infection, fatal doses of 

 diphtheria toxin were administered to guinea-pigs along 

 with such serum, but in no single case did the latter 

 survive, showing that this semni possessed no anti- 

 diphtheritic properties whatever, and was incapable of 

 protecting animals from diphtheria infection. 



Thus, on the one hand, we find that natural or race 

 immunity to a particular disease does not provide pro- 

 tective serum against infection from that disease in other 

 animals, .and, on the other hand, that the serum of 

 individuals who have never had diphtheria, does provide 

 in many cases such protective serum. 



Now Wassemiann argues from these facts that the 

 possession of protective human serum is not natural or 

 born with the indi\ idual ; for otherwise, as in the case of 

 white-rat-serum, it would be incapable of conferring im- 

 munity, that it must therefore rather be regarded as a 

 later acquisition, and subject to evolution processes. 



I n pursuing this line of reasoning, Wassermann assumes 

 that race immunity found to be characteristic of a parti- 

 cular description of animal is necessarily of the same 

 character as exceptional immunity confined to particular 



