Animal Resistance 



479 



Upon the basis of these findings, a further series of experi- 

 ments was undertaken by Louise Pearce and C. M. Van Allen 

 for the purpose of determining whether the course of the dis- 

 ease could be altered by operative interference with any of the 

 endocrine glands or by the administration of such chemical 

 agents as the iodides and mercury. Neither of these agents pos- 

 sesses any considerable spirocheticidal action in doses below the 

 lethal limits but have been found to produce marked changes in 

 the endocrine glands and the lymphoid tissues. 



These experiments are not complete but they show already 

 that, by either of the methods mentioned, the general character 

 and course of the disease may be greatly modified; that the re- 

 sistance of infected animals may be augmented or depressed by 

 one and the same agency; that the immediate effect is propor- 

 tional to the stimulation or depression of the activity of this 

 system of organs. In other words, it has been found that the 

 development and resolution of syphilitic lesions are subject to 

 the same influences as are concerned in ordinary processes of 

 growth and maturity. In this instance, it is of interest to note 

 that the lymphoid tissues act in harmony with the endocrines or 

 as though they formed a part of the general system of organs 

 concerned in these reactions. 



DISCUSSIONS AND CONCLUSIONS 



The experiments referred to open up an enormous field for 

 investigation. They supply us with a concrete basis for dealing 

 with phenomena of disease which are dependent upon animal 

 behavior. In fact, they point to the possible importance of this 

 system of organs wherever the factor of constitutional predis- 

 position or resistance enters into the problem of etiology or re- 

 sistance to disease. At the same time, the fact cannot be em- 

 phasized too strongly that we are dealing here with a system 

 of organs and tissues whose action may be interfered with at 

 a number of points and in a number of ways which in the end 

 may produce effects almost identical in character. In other 

 words, while it is obvious that one or another of the elements 

 of this system may be immediately responsible for a given effect, 

 or of greater importance than another, the integrity and sta- 

 bility of the mechanism and the existing balance in the functional 

 activity of its component parts appear to be the factors of 

 foremost importance. 



