542 SCIENCE PROGRESS 



halt was made until some similar but simpler cell-inclusions had 

 been examined, and observations were made on the blood of the 

 lower animals; for the finding of bodies is not sufficient in itself 

 to label them as the parasitic causes of disease, even when their 

 appearance is constant. 



The discovery of somewhat similar cell-inclusions in the 

 mononuclear cells of the blood of guinea-pigs, and which are 

 known as Kurloff-Demel bodies, led to the establishment of a 

 new genus of parasite called the Lymphocytozoa, because these 

 bodies were found (by the jelly method) to develop into 

 spirochaetes. These intracellular parasites stain in a very re- 

 markable manner on the jellies, and the development of their 

 nuclear material, even while within the substance of the cells, 

 can be observed very accurately. It was found that they pass 

 through a certain, constant, definite development into spiro- 

 chaetes while within the cells. It was also found that the 

 affected guinea-pigs frequently show signs of disease which are 

 similar to those seen in syphilis ; and the spirochaetes were dis- 

 covered free in the blood of these animals. The parasitic nature 

 of the cell-inclusions therefore was evident. 



Then J. W. Cropper of the McFadden Researches discovered 

 similar cell-inclusions in the male generative organs of earth- 

 worms ; these also were shown by him to develop into spiro- 

 chaetes and to pass through the same phases of development as 

 the guinea-pig parasite. This train of information was so 

 suggestive that a thorough examination of cases of human 

 syphilis was undertaken to see if similar intracellular parasites 

 were present in that disease also, which resulted in the finding 

 of them in every one of five hundred cases of syphilis examined. 

 They have been seen in all the lesions of the disease — those of 

 the primary, secondary, and tertiary stages ; and they have been 

 demonstrated by the jelly method to develop into spirochaetes 

 which resemble the Spirochceta pallida. But it was noted also 

 that there were other forms of the parasite, namely, free amoeboid 

 bodies, and various other phases were recognised in the circu- 

 lating blood of syphilitics ; this led to the suggestion that the 

 spirochaetes really represented gametes, or male elements of a 

 large and complex parasite. Phases which may well be the 

 female elements have been seen in both guinea-pigs and in 

 human beings, and conjugation has been observed in the 

 former ; but this aspect of the question remains for the present 



