THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL, 



Vol. XII OCTOBER, 1891. No. 10. 



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Trichina Spiralis. 



By Dr. H. M. WHELPLEY, Ph. G., F. R. M. S., 



ST. LOUIS, MO. 



The Trichina spiralis is one of the most interesting of the entozoa 

 (animals living within another). It is classified among the namatoid 

 (thread like) helminths (worms) , and derives its name from a resem- 

 blance to a spirally twisted hair. 



Description. — The individual worm as found in the flesh of animals 

 is asexual and varies in size from 34S to 1270 micromillimeters (1-73 

 to I-30 inch) long by 26 to 40 micromillimeters (1-960 to 1-640 inch) 

 thick. 



Trichinae have been found in human beings, hogs, cats, dogs, rats, 

 mice, badgers, hedgehogs, eels, moles, and chickens. It is reasonable 

 to suppose that they may occur in any carnivorous animal. After the 

 animal has been infected with the parasite for a time varying from a 

 few months to one or two years, the helminths become incapsulated 

 with a hard calcareous lemon-shaped cyst. This is probably a con- 

 servative act of nature to protect the muscle from the foreign body and 

 the trichina remains passive in the process of encysting. Some authori- 

 ties state that the cysts from human flesh can be distinguished from those 

 found in hogs on account of having a nodule at each end of the capsule, 

 but I have been unable to verify the statement. The worms may be 

 present in flesh to the extent of over two hundred thousand to the cubic 

 inch. During the stage of existence just mentioned the trichinse are in 

 a condition to live as long as their host retains vitality. After the death 

 of the animal forming their home, the little fellows will survive many 

 trials of hardships. Maceration in water does not aftect them, even 

 when continued for weeks. They have been known to survive a tem- 

 perature of 165'^ F., and at 25 degrees below zero became quite active 



Copyright, 1891, by C. W. Smiley. 



