GENERAL PHYSIOLOGY 195 



any type of nutrition of free-living forms with the exception of auto- 

 trophic nutrition, and even this seems possible with intestinal para- 

 sites of the tadpole (Hegner, 1923; Wenrick, 1924). Holozoic 

 nutrition, or the engulfing of solid particles of protein substance, is 

 found in Endamceha dysenterice, Craigia Jiouiinis, etc., which ingest 

 bits of tissue and red blood corpuscles. The equivalent of saprozoic 

 nutrition, called osmotic nutrition by Doflein, is a more common 

 form. It is quite possible, although not proved, that some parasites 

 such as the pathogenic amcebte, secrete proteoclastic ferments 

 which digest tissue elements outside of the amoeba protoplasm and 

 then absorb the digested product by osmosis. Such a process might 

 account for the characteristic lesions in the liver or intestine during 

 amoebic dysentery. The majority of protozoan parasites, however, 

 apparently live upon the products of digestion as prepared by the 

 host, the digestive tract being in effect one huge gastric vacuole. 

 Many intracellular parasites intercept similar digested food material 

 destined for tissue cells at the end stage of its journey fCoccidia, 

 Hsemosporidia, ha^moflagellates, intracellular flagellates, ]\Iyxo- 

 sporidia, etc.). Others live upon products of tissue metabolism 

 which are absorbed by osmosis, as in lumen dwelling forms, or on 

 products of cell activity as in hemoglobin absorption by malaria 

 organisms, Babesias, etc. In such cases, it is unknown whether the 

 parasite selects particular substances from its environment, or 

 prepares its food by the secretion of digestive fluids. 



Specific structural adaptations, useful in such methods of food- 

 getting, are characteristic. Haustoria-like processes, derived from 

 the epimerites of gregarines, in some cases extend deeply in the 

 tissue cell {Stylorhyncus kmgicollis, Echinomeru hispida, Py.vinia 

 mcehmszi, etc., Fig. 93). The coccidian Caryotropha mesnili, 

 according to Siedlecki, shows a significant relation between the 

 nucleus of the host cell and that of the parasite. This organism is 

 a parasite in the spermatozoa of the annelid PoJymnia nchulosa 

 where the sperm cells are aggregated in bundles in the character- 

 istic annelid fashion, usually about a feeding mass or blastophore. 

 The parasite gets into such a cell as an agamete or sporozoite, 

 one only of the biuidle, as a rule, being infected, and as it grows 

 the nucleus of the cell is displaced to one side and the cell loses its 

 characteristic structure, becoming hypertrophied and distorted 

 (Fig. 93, 2). Not only the infected cell but all the other cells of the 

 spermatogonia bundle are affected, and none of them continues the 

 normal de^•elopment, but they become arranged like epithelial cells 

 about the hypertrophied infected cell. 



The specific eff'ect of the young Caryotropha on the infected cell 

 consists not only of the enlargement of that cell, but of a definite 

 feeding mechanism by which the parasite is supplied with food. 

 That the nucleus is a center of constructive metabolic changes is 



