Occurrence. Etiology. 817 



According to the investigations of Tenipel and otliers, trichina; occur in some 

 neighborhoods to a greater extent in slaughtered dogs (in four years on an average 

 1.11%), than in swine (of 289 slaughtered dogs Tempel found four with trichinae 

 [1.4%-]). In the year 1906 trichinosis was found in 0.222 7o of slaughtered dogs. 



In swine imported from Hungary into Saxony trichinae were found in 



0.011% in 1893; in 1894, 0.009%; and in 1895, 0.024% (Ostertag) ; recently 

 imported from Austro-Hungary have been found to be more subject to trichinae 

 than the native breeds (Edelmann). 



Trichinosis is much more frequent in North America. Thus Billings found 4% 

 and Salmon 2.7% of swine in Boston to be affected with trichina?. In the year 

 1874 the percentage in Indiana was l(i..3, later 6.5 ; in Chicago, in the year 1878, 

 8%; in 1883, 2.4%; in 1881, in New Orleans, 0.4%. According to Hamel-Eoos, in 

 Boston, from 1886-1890, out of 3,064 swine examined, the boars were infected in 

 14.87% of cases, and the sows in 10.61%.. Of American hams and other pig 

 products imported into Germany, an average of 2-3% (maximum 8%) were found to 

 be trichinous (Friedberger & Frohner). 



Etiology. The Trichina spiralis (Trichinella spiralis) is a 

 small nematode belonging to the family of Trichotrachelides 

 (see page 487) which occurs in the body of susceptible animals 

 and of man and causes the disease. It occurs in a sexually 

 mature state in the intestinal canal, and as larvae in the muscu- 

 lar tissue. 



The intestinal trichina is barely visible to the naked eye as a very fine, thread- 

 like, yellowish white worm, whose straight anterior end becomes gradually thinner, 

 while the blunt hind end appears bent. The surface of the body is flat with fine 

 cross stripes; the male 1.4 to 1.6 mm. long, 0.04 mm. thick; the female 3 to 4 mm, 

 long, 0.06 mm. thick. From the fertile eggs, with a diameter of 0.02 mm., embryos, 

 about 0.12 mm. long, develop in the uterus of the female. They break through 

 the eggshell in the uterus and are born alive. The male dies after copula- 

 tion, but the female remains alive until after the birth of the embryos; her average 

 duration of life is 5 to 8 weeks. 



The muscle trichina at first lives free inside the sarcolemma of the muscle 

 fibres, then rolls up and becomes enclosed in a lemon-shaped capsule. It is 0.7 to 

 1.0 mm. long, its head end forms a point, and its hind end is blunt. 



The development of trichinae occurs as follows : After the eating 

 of flesh containing the encapsulated, living muscle trichinae the capsule 

 is dissolved by the gastric juices within 18 to 20 hours, and the liber- 

 ated larvae reach the small intestine after 30 to 40 hours; they grow 

 quickly, and in about 2i/'o days become sexually mature. Five days 

 after copulation, after the female has been pressed into Lieberklihn's 

 glands along with the male, she deposits living embryos in the interior 

 of the glands. During a residence of 5 to 8 weeks a single female can 

 produce, according to Braun, 8.000 to 10,000, and according to Neu- 

 mann 15,000 embryos. 



From Lieberklihn's glands the young trichinae reach the lymphatics 

 on the seventh day, according to the investigations of Cerfontaine, Geisse, 

 Askanazy, and especially Graham; from there they pass to the tho- 

 racic duct and finally reach the blood stream, where they are deposited 

 by the capillaries in different tissues, and there become arrested. Since 

 the trichina embrj'o has been observed to have a spike-like process at 

 the anterior of its body, Hoyberg considers that it is capable of wan- 

 dering actively from the intestine. As soon as the embryos reach the 

 tissues of a convenient organ they develop there further if the con- 

 ditions are favorable. The socalled wandering trichina going with 

 the lymph stream into the lymphatic glands, and with the blood stream 

 into ^ the rest of the organs soon perish, but those reaching the 

 striated muscles which contain sarcolemma persist. The wandering 



