THE PATHOGENIC RHIZOPODA 299 



able, usually spherical, and without much change in position during 

 the activities of the body, that of E. histolytica is highly variable, bend- 

 ing and turning with contact with objects in the cell, or flattening into 

 a disk in the cortical plasm. 



The ordinary vegetative increase of Entameba histolytica takes 

 place by simple division or by budding on the periphery, the formation 

 of eight spores never being seen. Division takes place while the 

 organisms are lying between the cells of the gut tissues, and may be 

 either equal or unequal, the unequal division passing by imperceptible 

 grades into bud formation. The buds are apparently similar in their 

 mode of formation to those of acanthocystis (see p. 31), the nuclei 

 arising, according to Schaudinn, by amitosis (Fig. 32, p. 94.) 



Permanent cysts are not formed during the height of the disease, but 

 are first found during periods of healing, and after the organisms have 

 reproduced again and again by division. The beginnings of the 

 preparations for spore formation are first manifested in the nucleus. 

 Here the peripheral zone of chromatin granules becomes thicker, the 

 membrane of the nucleus disappears and the granules are ultimately 

 disseminated throughout the protoplasm in a typical chromidium 

 form similar to that of centropyxis (see p. 150), while the residual 

 nuclear parts, with some protoplasm, degenerate. Spores are formed 

 by the protrusion on the surface of the cell of small buds containing 

 chromidia, and these buds are transformed into spores by secretion 

 about themselves of a definite resisting membrane, while the central 

 protoplasm, with the residual nucleus, degenerates. The further his- 

 tory of these buds was not ascertained by Schaudinn beyond the fact 

 that they were capable of infecting normal cats with amebic dysentery, 

 so that the processes of conjugation are still unknown. It will be an 

 interesting study for some student of the group to see if conjugation 

 follows the pattern of Entameba coll or that of centropyxis, where the 

 idiochromidia bearing spores are gametes which unite after leaving the 

 parent cells. 



It is not the place here to discuss the question whether or not these 

 parasites of the human intestine are the causes, or the sole causes, of 

 acute enteritis in man. 1 Pathologists, in the main, are in accord that 

 one type, at least, of dysentery is traceable to these rhizopods, but 

 there is a difference in opinion as to whether the rhizopods create an 

 enzyme or poisonous product which acts as a direct agent on the tissues, 

 or whether they are passive in this respect, but cause mischief by the 

 mechanical irritation of their movements between the cells. Shiga 

 and Flexner have shown that one type of dysentery is to be traced to a 

 bacillus, and Prowazek suggests that these parasitic ameba? may play 

 an important part as carriers of bacteria into the deeply lying tissues 



1 Prowazek has recently given evidence to support the view that flagellates of the genus 

 Lamblia megastoma (Fig. 115) are capable of causing acute intestinal trouble of like nature. 



