510 



SCIENCE 



[N. S. Vol. XXXII. No. 824 



has been added to existing knowledge, and the 

 expensive work done in the form of experi- 

 ments is worthless to future investigators, be- 

 cause the authors have failed to keep apart 

 ordinary coecidiosis and the parasite produc- 

 ing the specific csecal and liver lesions. Even 

 though subjectively convinced of the truth of 

 their hypothesis, they should have objectively 

 recorded the lesions and kinds of parasites 

 found in the subjects of their experiments, so 

 that others, who refuse to accept their hypoth- 

 esis, might still have utilized the results. We 

 have now a report which is neither one thing 

 nor the other; it is neither on coecidiosis nor 

 on entero-hepatitis. 



When I first heard of entero-hepatitis as a 

 " coecidiosis," I went over all the material 

 from cases of the disease then in the labora- 

 tory to endeavor to read if possible this new 

 hypothesis into the facts, although I had al- 

 ready stated in my early report (1895) that 

 " it is very improbable that these bodies 

 (coccidia) stand in any genetic relation to the 

 true micro-parasite of the disease." This re- 

 cent enquiry, however, carried me still farther 

 away from this new hypothesis. 



The weakness of the position taken by Cole 

 and Hadley can be easily grasped by readers 

 who are not protozoologists and pathologists 

 when put in possession of a few fundamental 

 facts. It has been the experience of micro- 

 biologists for the past thirty years that when 

 a disease which is apparently due to a certain 

 causative organism shows now one type of 

 lesion, now another, now the presence of the 

 suspected organism, now its absence, two in- 

 fectious agents are involved which may work 

 together or separately. 



Whenever microorganisms can not be 

 studied in pure culture artificially the infec- 

 tion with the products of disease may lead to 

 double or even triple infections, because two 

 or even three parasites may be in the infect- 

 ing material. The same may occur spontane- 

 ously in any restricted territory where several 

 diseases have coexisted for years. Most ani- 

 mals living in such locality may become the 

 victims of several diseases. The only way out 

 of the difficulty is to study the disease as it 

 occurs in widely separated localities. If it 



can be shown that outbreaks of entero-hepa- 

 titis may occur without coccidia and that out- 

 breaks of coecidiosis may occur without liver 

 disease and the presence of A. meleagridis, 

 we have cleared away most of the dilficulties 

 surrounding the interpretation of a dual in- 

 fection. Let us see what facts we can bring 

 together bearing on this phase of the subject. 



In 1894 I examined animals from nineteen 

 farms, but only on two was coecidiosis pres- 

 ent. This spring I examined a small flock of 

 young turkeys kindly incubated and reared 

 for me by Dr. Austin Peters. Though six out 

 of nine of this flock died of " blackhead," 

 without being exposed to any disease so far as 

 we can discover, not a single coccidium was 

 found either in the diseased or in the healthy 

 animals. By a stretch of imagination it 

 might be claimed that coccidia had not time 

 to mature in these animals, which either died 

 or were killed in from four to ten weeks after 

 hatching. But as I have seen mature coccidia 

 cysts in turkeys four weeks old this argument 

 can not be used. 



Although avian coecidiosis has been known 

 since 1878, it is strange that close observers 

 like Eivolta and many subsequent writers fail 

 to report lesions of the liver which are so 

 characteristic of the entero-hepatitis of turk- 

 eys. Surely this striking lesion would not 

 have escaped even the most cursory and 

 superficial examination. The authors in their 

 recent report fail to distinguish between 

 coecidiosis of the liver in which the epithel- 

 ium of the bile ducts is the seat of the inva- 

 sion, and the embolic, blood infection of the 

 turkey's liver in which the parenchyma alone 

 is affected. I do not recall any description of 

 either type of liver disease in the coecidiosis 

 in birds, although there is no reason why 

 liver coecidiosis might not be found in birds 

 as in rabbits. Leaving, however, aside this 

 important distinction, let us see what the au- 

 thors say of " coecidiosis " in other birds (on 

 page 180 of their recent report). In four 

 guinea-fowls, coccidia were present in either 

 intestines or cseca, hut there were no liver 

 lesions." In two out of five ducks, coccidia 

 were present in the caeca tut not in the liver. 



' Italics mine. 



