INOCULATION INTO LOWER ANIMALS. 347 



over with a low-power objective, one will notice at 

 irregular intervals little masses that look in every re- 

 spect like particles of staining-matter which have been 

 precipitated upon the section at that point. When 

 these little masses are examined with a higher power 

 objective they will be found to consist of small ovals or 

 short rods so closely packed together thai the individuals 

 composing the clump can often be seen only at the very 

 periphery of the mass. This is the chai-acteristic ap- 

 pearance of the typhoid organism in tissues. The little 

 masses are usually in the neighborhood of a capillary. 



Result of Inoculation into Lower Animals. — 

 A great many experiments have been made with the 

 view of reproducing the pathological conditions of this 

 disease, as seen in man, in the tissues of lower animals, 

 but with limited success. Fatal results without the 

 appearance of the typical pathological changes have 

 frequently followed these attempts, but in most cases 

 they could easily be traced to the toxic/ rather than to 

 the truly infective' action of the materials introduced 

 into the animals. 



The most successful efforts for the production of the 

 typical typhoid lesions in lower animals are those re- 

 ix)rted by Cygnaeus. By the introduction of the 

 typhoid bacilli into the tissues of dogs, rabbits, and 

 mice he was able to produce in the small intestine con- 

 ditions that were histologically and to the naked eye 

 analogous to those found in the human subject. 



Of a large number of experiments made by the writer 

 with the same object in view, only one positive result 



1 Toxic— Poisonous results not necessarily accompanied by the growth of 

 organisms throughout the tissues. 



- Infective or septic— Poisoning of the tissues as a result of the growth of 

 bacteria within them. 



