512 



SCIENCE 



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



rejects the identity of submucous cysts and 

 psorosperms for the following reasons : 



1. The, psorosperms always inhabited the 

 epithelial cells, the gregarines the submucous 

 connective tissue. 



2. There were fowls which contain thou- 

 sands of psorosperms but no gregarine^. 



3. There were found young chickens, -black- 

 birds and crows with gregarinosis without 

 showing any psorosperms. 



Eivolta's example might well be followed 

 by ovir younger scientists. It is easier for 

 the time being to make all forms over into a 

 single species but in the end it is likely to 

 lead to nothing. Eivolta, by the way, says 

 nothing of liver lesions. 



Another instance of the possible presence 

 of two distinct parasites constituting what 

 has for eighteen years been regarded as one, 

 has recently been discussed by A. Theiler." 

 Theiler thinks that what has hitherto been 

 regarded as a single blood corpuscle parasite in 

 Texas cattle fever represents two. In the first 

 report'" on this disease both forms were shown 

 to appear in the blood of cattle which had re- 

 ceived a single injection of blood from a 

 southern animal. Both live within the red 

 cells, one type appearing first in the course of 

 the disease, then the other. Theiler argues 

 with much force that there are two species 

 involved because in some parts of the world 

 one type alone was reported as present in the 

 blood of diseased animals, in other parts, the 

 other type. In our own country both types 

 occur. Without accepting for the moment 

 Theiler's views, which I have not yet studied 

 in detail, I think they are suggestive and 

 worth careful attention. Fortunately in our 

 report these types have been noted separately 

 in the protocols, so that even after eighteen 

 years the records are available for an analysis 

 of Theiler's position. 



Among the other blemishes of a work which 

 otherwise shows much industry and study and 

 a commendable care in editing is the use of the 

 term Coccidium cuniculi and the suggestion 



" Ztschr. f. Infektionskrankheiten d. Haustiere, 

 etc., 1910, 8, p. 39. 



" Smith and Kilborne, " Investigations into the 

 Etiology of Texas or Southern Cattle Fever," 

 Washington, 1893. 



that there is any direct relation between the 

 coccidium of the rabbit and that of birds. 

 To assume that a species which rbfuses to in- 

 vade near mammalian relatives and which 

 seems to cling to the rabbit host throughout 

 the world should have a closer relationship or 

 even be identical with the avian coccidium 

 seems to be attributing to nature a fickleness 

 which students of parasitism know only too 

 well does not exist. So clearly defined and 

 narrow is the range of parasites even in the 

 same host that it is with difficulty that coc- 

 cidia locate in the epithelium of the large 

 intestine when the epithelium of the upper 

 small intestine has been preempted. The 

 statement should therefore have been based 

 on some actual experiments on birds with 0. 

 cuniculi of the rabbit. 



In order to avoid misunderstanding in 

 making this criticism, I wish to state emphat- 

 ically that I do not regard my early work as 

 in any sense complete. The questions con- 

 cerning the amcebic character" of the bodies 

 I described, the simple or complex nature of 

 their life cycle, the direct, indirect or inter- 

 mediate mode of infection do not come into 

 consideration. Whatever position concerning 

 one and all of them I had taken may be dis- 

 puted as long as the life cycle has not been 

 satisfactorily worked out. The final solution 

 of these questions can be reached only after 

 years of experimental breeding and rearing 

 in carefully guarded territories on which no 

 poultry is kept and from which even game 

 and other wild birds are excluded. My 

 criticism is confined to the confusing of an 

 old well-known with a new and poorly known 

 protozoan parasite and the consequent use- 

 lessness of the investigation as a basis for 

 further work. I also wish to protest against 

 the publication of premature, undigested, 

 controversial statements in the form of pre- 

 liminary notices years before the appearance 

 in print of the actual work on which such 

 statements are presumably based. 



Theobald Smith 



Habvaed Medical School, 

 September 20, 1910 



^^ Amffibic changes in form have been noted re- 

 cently in liver tissue examined immediately after 

 chloroforming affected turkeys. 



