1881.] 



MICROSCOPICAL JOURNAL. 



47 



or from the swine, and not the swine 

 from the rats. If this is true, we are 

 no nearer solving the question as to 

 how swine become infected, than we 

 were before the trichinae were found 

 in rats. Some hog-keepers say that 

 they have seen swine hunt and kill 

 rats, while others assert that such a 

 thing never takes place ; but they all 

 admit that a hungry hog would un- 

 doubtly eat a rat if it had it. Admit- 

 ing that hogs may become infected 

 from eating a trichinous rat, we have 

 still before us the questions : — 



I. Is this the only source from 

 which swine become infected ? 2. Is 

 there no common source from which 

 not only they, but wild animals, es- 

 pecially omnivora and carnivora, may 

 become infected ? 



As American pork, and, according 

 to my observations, American rats, 

 are much more infected than similar 

 animals in Germany, it seems as if 

 here in America were the place to 

 decide these important questions. 



The Microscopic ^Examination 

 OF Pork. — Numerous elaborate es- 

 says have been written upon this 

 subject, but the entire process is so 

 easy and simple that such extended 

 labor can well be looked upon as 

 useless. Almost the first, and at the 

 same time by far the most profusely 

 infested muscles, are the so-called 

 " pillars of the diaphragm." The same 

 are to be always found, as two small 

 stumps of flesh immediately above 

 the kidneys in the dressed hog, when 

 hung up to "cool out." If there is a 

 single trichina in the organism, it is 

 probably to be found there. These 

 pieces belong to the trimmings, and 

 are always to be had without in the 

 least disturbing the appearance of the 

 hog. The next step is, to take the 

 piece of muscle to be examined, and, 

 if at all dried, to make a fresh cut 

 into its substance, then with the cur- 

 ved scissors cut one, two, or three 

 thin slices lengthways to the fibres, 

 i. e., with them, and with a needle 

 place them upon the object-glass a 

 little distance apart ; the covering 



glass is then placed upon them, and 

 gently pressed with a slight rolling 

 motion in one direction and back if 

 neccessary. This will make the sec- 

 tions thin enough for examination. 

 The free trichinae, as shown in Fig. 

 9, are seldom found in swine, as 

 they are not often examined after a 

 fresh invasion. 



To determine if the trichinae still 

 live, place the object-glass over a 

 spirit-lamp, heat a second, and then 

 place again upon the microscope, and 

 they will be frequently seen coiling 

 themselves in their capsules. It is 

 better, however, to finely tease out 

 the preparation first, when individ- 

 uals will frequently become freed 

 from their capsules, and their move- 

 ments can be better observed by the 

 application of heat. Salted pork is 

 best examined by taking the cuts 

 from the scissors, and soaking them 

 in fresh water for a second or so be- 

 fore pla'cing upon the slide. They 

 press out much easier and thinner, 

 when such a procedure is resorted to. 



Fig. 15. — Deposit of Tyrosin crystals in ham. 

 (Leuckart.) 



Objects which may be mis- 

 taken FOR Trichina or not 

 recognized as such. — There are 

 some possible sources of mistake in 

 examining for trichinae, as indicated 

 below, but which can readily be 

 avoided with care. It not unfre- 

 quently hapi)ens that the capsules of 

 the parasites formed by the sarco- 

 lemma, or embracing membrane 

 of the muscle-fibres, become abnor- 

 mally thickened, the trichinae being 



