﻿NO. 8 RECOVERS FROM INFECTION FLEXNER II 



But the problem is not solved with the discovery of a specific 

 serum or chemical, since these perfected agents must act within the 

 body upon the parasitic causes of disease that seek in different ways 

 to escape their influence. Whether the parasites have a general dis- 

 tribution throughout the blood and tissues, or whether they are con- 

 fined within a pathological formation in the interior of an important 

 organ or part, and whether they can resist by mutational alterations 

 the action of the curative agents, may be the factors that determine 

 whether the native curative principles or the extraneous ones shall 

 gain access to the seat of disease and bring about their suppression. 



In its struggle to survive, the parasite withdraws sometimes into 

 situations to which the curative substances gain access imperfectly 

 and with difficulty. This is the condition present in local infections 

 more or less cut off from the general circulation and from the cura- 

 tive principles purveyed by the blood and met with in the great 

 serous cavities, and especially in the cavity within the membranes 

 that surround the central nervous system. The cerebrospinal fluid- 

 is a remarkable liquid that may be regarded as the " lymph " or nutri- 

 ent medium of the central nervous system; and yet it is almost 

 devoid of protein matter. Now, as it is the protein matter that carries 

 the immunity and healing principles, it follows that the subarachnoid 

 spaces of the central nervous system are dangerously free from 

 them. Moreover, since the anatomical structure decides the quality 

 of the lymphatic fluid in health, it also determines it in disease, and 

 thus it follows that parasites that become localized in the cerebro- 

 spinal membranes, for example, are insured a potential advantage 

 against the host. And these general facts are applicable, if in some- 

 what less degree, to parasites that become established in the cavity 

 about the heart, the lungs, and the abdominal viscera, as well as the 

 spaces about the joints. 



Again, certain parasites possess a power of regulation within 

 themselves that serves, often, to protect them from extinction. Under 

 the influence of specific serums or drugs, they undergo a subtile 

 change, probably chiefly of a chemical nature, through which they 

 acquire a capacity of effective resistance to the curative agent. This 

 state is called " fastness " and is regarded as a kind of mutation 

 equivalent to the sudden formation of " sports " and new species 

 among the higher plants and animals. The acquired characters 

 of fastness have been observed to be transmitted by certain orders 

 of parasites through indefinite generations. Our knowledge of this 

 state is derived chiefly from the study of trypanosomes and spiroche- 



