November 23, 1883.] 



SCIENCE. 



677 



Bacilli were found in all the fresh cholera cases, but 

 were wanting in the case where death had occurred 

 after the symptoms of cholera had disappeared, and 

 in others where death had not occurred from cholera, 

 in wliich examinations were made for the sake of 

 comparison ; so that there can be no doubt that these 

 organisms liave some connection with that disease. 

 But it is too much to conclude yet that bacilli are the 

 cause of cholera because they are found in the mu- 

 cous coat of the intestine of cholera p.atients. The 

 inference might be reversed; and we might say that 

 the disease produces such changes in the mucous 

 coat, that some of the many bacteria present there as 

 parasites are able to penetrate the tissue. A decision 

 of the question, which of the two views is correct, — 

 whether the infection or the bacteria invasion comes 

 first, — can only be settled experimentally by collect- 

 ing the bacteria from the diseased tissue, breeding 

 them by ' pure culture,' and then reproducing the 

 disease by infection experiments on animals. For 

 this purpose it is necessary, first of all, to have such 

 animals at our disposal as are susceptible to the in- 

 fectious matter; but in spite of every etl'ort to infect 

 animals with cliolera, it has not yet been demon- 

 strated that they can be made to take that disease. 

 Experiments Iiave been tried with rabbits, guinea- 

 pigs, dogs, cats, monkeys, pigs, rats, etc., but always 

 without success. The only statements to the con- 

 trary, worthy of notice in this connection, are the 

 accounts of Thierscii's experiment with mice wliich 

 he fed with the contents of the intestine of a cholera 

 patient, and which were tlien attacked with diarrhoea, 

 and died. This experiment has been confirmed by 

 reliable experimenters, like Burdon-Sanderson, and 

 has been criticised, and the conclusions drawn from 

 it disputed by others. We considered it necessary to 

 repeat this experiment because it was of the utmost 

 Importance for our purpose to discover some species 

 of animal capable of infection witli cholera. 



I'Varing that tlie reiiuisite number of mice could not 

 be obtained at once in Alexandria, we carried fifty of 

 those animals with us from Berlin, and began the 

 infection experiments with them. We also experi- 

 mented with monkeys, — because they are tlie only 

 animals susceptible to certain human diseases, sucli as 

 small-pox and relapsing fever, — and, besides these, 

 with a few dogs and chickens. But, in spite of all 

 our care, the experiments were failures. The most 

 varied samples of vomited matter, choleraic dejec- 

 tions, and contents of the intestines from bodies of 

 persons dead of cholera, — sometimes fresh, some- 

 times after standing some time in a cool or warm 

 place, and sometimes in a dried condition, — were 

 fed to these animals; but no symptoms of cholera 

 appeared, and they remained perfectly healthy. 



Besides tliis, 'pure culture' experiments were 

 made with bacilli taken from the contents of the 

 intestine and its walls. The material obtained in 

 this way was fed to the animals, and inoculation 

 was also tried. This latter method, with the products 

 of the ' pure culture,' sometimes produced septic dis- 

 eases; but no symptoms of cholera appeared. 



That the material of the disease is very often con- 



tained in the dejections of cholera patients in .an ac- 

 tive form, is shown in several ways, and particularly 

 by the frequency of the disease among washerwomen 

 who wash clothes soiled with such dejections. A 

 case in point occurred during tlie present epidemic 

 in the Greek hospital, where a washerwoman who 

 washed for the cholera hospital exclusively was taken, 

 with the disease. It is therefore certain, tliat, of the 

 numerous samples used in our experiments, some 

 at least must have contained the infectious matter. 

 But since our experiments were failures, it must be 

 assumed, either that the animals we used are not 

 susceptible to cholera, or that we had not discovered 

 the right method of producing infection. At any 

 rate, the experiments ouglit to be repeated and modi- 

 fied; but, with the material now at our command, 

 there is little prospect that they would prove suc- 

 cessful. 



Our want of success may possibly be explained in 

 still another w.ay, wliich is this. In a place visited 

 by the cliolera it is usual for the disease to cease 

 before all the inhabitants have been attacked; and, 

 although the infectious material is scattered about 

 in great quantity, fewer and fewer persons are affected 

 by it, and the epidemic at last dies out in the midst 

 of individuals callable of taking it. This circum- 

 stance can only be explained on the theory that the 

 infectious matter loses its activity, or at least be- 

 comes uncertain in its action, towards the end of the 

 epidemic. If, therefore, human beings become less 

 su.«ceptible to the infection of cholera towards the 

 end of the epidemic than at its outbreak, it can 

 hardly be assumed that the animals used for exjieri- 

 ment, of whose susceptibility to infection we know 

 nothing, should differ from tliem in this respect. 

 And for our experiments we could only obtain mate- 

 rial which had been collected towards the end of the 

 epidemic, and which must be presumed to have been 

 more or less inactive. It is of course possible, tliat 

 under suitable conditions, such as the outbreak of 

 a cholera epidemic, the infection of animals with the 

 disease miglit be successfully accomplished ; and such 

 would be the proper time to determine by experi- 

 ment whether the bacilli I observed in the mucous 

 coat of the intestine constitute the true cause of 

 cholera. 



However far the commission may still be from a 

 complete solution of the problems proposed to it, 

 and although its labors have contributed little which 

 may prove of practical value in combating the chol- 

 era, yet, considering the unsatisfactory conditions 

 under which the experiments were made, and the 

 short time the commission was able to devote to 

 them, the results thus far obtained should be re- 

 garded as encouraging. The experiments fully an- 

 swer the original purpose of localizing the disease, 

 and, by ascertaining the constant presence of char- 

 acteristic micro-organisms, have supplied the first 

 condition for the investigation of infectious diseases, 

 and afforded a determinate object for further re- 

 search. 



From the foregoing statements, it is clear that the 

 commission can accomplish no more in Alexandria 



