Suscei)til)ilily. Anatomical riian^es. 819 



Dogs wliicli also frequently suffer from trichinosis in- 

 fect themselves by eating rats which they catch. The same is 

 true of polecats, while the infection of wild swine, foxes, bad- 

 gers, hedgehogs, martens and marmots takes place by eating 

 mice. 



Susceptibility. In respect to susceptibility there is no dif- 

 ference between the various breeds of pigs. The spread of 

 trichinosis, however, varies greatly in different neighborhoods, 

 and in this respect the breeding and management of animals 

 has a great influence. Infection through trichinous swine flesh 

 and through rats occurs very easily where no great importance 

 is attached to cleanliness and the burying of dead animals is 

 not carried out immediately, where, further, parts of the bodies 

 of dead swine are fed to others. At the same time there is more 

 opportunity for infection where the swine are not reared in 

 the open air and in large herds, but are kept in sties in the 

 neighborhood of dwelling houses. 



Many other animals are also susceptible to trichinosis, 

 such as the wild hog, mice, dogs (Tempel found trichingB in the 

 flesh of slaughtered dogs as often as in that of swine), cats, 

 wolves, bears, badgers, etc., horses, cows, sheep, rabbits, guinea 

 pigs and hares can be infected artificially. 



The susceptibility of differeut species of animals is not equally great. Mam- 

 malians are the most susceptible, while in birds only intestinal trichinae develop, but 

 the young trichinae soon disappear in the intestine. Genersich accounts for this dif- 

 ference by the fact that the chemical- composition of the intestinal contents are 

 always alkaline in rabbits, and frequently so in man, rats and mice, especially after 

 hunger, while in dogs and birds (ducks) the intestinal contents show an acid re- 

 action. It follows that the susceptibility of warm-blooded animals is in inverse 

 ratio to the acid reaction of the intestinal contents. 



Anatomical Changes. After the first week only a certain 

 watery consistency of the muscular tissue is found; besides 

 the cut surface appears somewhat cloudy, its color pale and 

 transparent gray. From the fifth to the tenth week the muscle 

 fibers, when cut in their long direction, show very fine gray or 

 yellowish streaks, while somewhat later one sees very small 

 yellowish gray, or grayish white little specks thickly clustered 

 together or strewn about, which stand out sharply defined when 

 examined against the light. The respiratory muscles such 

 as the diaphragm and intercostal muscles are attacked most 

 severely, also the muscles of the neck, larynx and tongue. 

 (According to Bohm the muscles whose activity is the most 

 intense are attacked most severely.) Within the muscles the 

 trichinae are found in greatest numbers in the superficially situ- 

 ated fibers and in the neighborhood of tendons, while the tendons 

 themselves remain quite free from the parasites. In the heart 

 muscle and in non-striated muscular tissue trichinae never occur 

 (no sarcolemma!). 



