PATHOGENESIS. 93 



Theoretically, the blood and organs of healthy animals 

 contain no germs, yet we must accept the fact that often 

 solitary streptococci, tubercle bacilli, etc., are present in 

 the healthy body, circulating in the lymph- and blood- 

 stream and becoming fixed at loci minoris resistentiae, 

 from which places they extend further. Perez found, in 

 a systematic examination of healthy bodies, that only the 

 lymph-glands contain bacteria, but here the bacterial flora 

 was very rich. * In dead animals after sixteen to twenty 

 hours at room temperature or after five to six hours in the 

 incubator, bacteria are found in the blood and organs 

 (Trombetta), having for the greater part wandered from 

 the intestine. In the most frequent artificial method of 

 infection, i. e., subcutaneous injection, the bacteria are 

 absorbed through the lymph-stream, and in part are held 

 back in the lymph-glands, weakened in their virulence 

 and even killed ; but if the organisms are strongly ' ' path- 

 ogenic," they resist total destruction, and, on the contrary, 

 begin to increase a few hours after entrance. Regarding 

 the method of destruction of bacteria, compare page 97. 



Wherever we inspect the character of the pathogenic 

 action of bacteria, they are found to operate through chem- 

 ical substances which they produce or which are produced 

 from them in the animal body. Thus far we are able to 

 understand the action of only those bacteria which in cul- 

 tures form poisonous substances, by means of which we 

 can also reproduce the characteristic picture of the disease 

 more or less accurately. Bacteria of this class are : Bac. 

 tetani and Corynebact. diphtherias, Streptococcus pyo- 

 genes, Micrococc. pyogenes, Vibrio choleras, etc. There 

 has already (p. 73) been given a sketch of what we know 

 chemically about these poisonous substances. 



On the contrary, the means for an explanation upon a 

 chemical basis are almost entirely absent as yet in a series 

 of important infectious diseases, among which are, for ex- 

 ample, anthrax (Conradi, Z. H. xxxi, 287) and swine 



1 It may be mentioned here that often a considerable number of mi- 

 cro-organisms are also rapidly secreted through the bile and urine with- 

 out any perceptible injury to the organ being demonstrable (Biedland 

 Kraus, Z. H. xxvi, 353), yet many authors assume, in these cases, at 

 least microscopic rupture of vessels (Opitz, Z. H. xxix, 505). 



