IGG BOARD OF AGRICULTURE. 



advance the science of lielminthology. He corrected his own pre- 

 viously-expressed opinion on the validity of Kiichenmeister's obser- 

 vation on the transformation of the flesh-worm into trichocephalus^ 

 and thus confirmed Virchow. He also showed that the 30ung tri- 

 chinne in the intestines became the enc3'sted worm in the mustles, 

 and he believed that the}' readied there by migration through the 

 tissues, as graphicall}' illustrated in Kestner's circular figure, on our 

 fine lithographic plate. Others, however, claim that the distribution 

 of the trichina} over the body in so short a time can only be effected 

 through the circulation of the blood. 



NATURAL HISTORY OF THE PARASITE. 



These famous microscopic entozoa that so frequently contaminate 

 our pork, and are known among naturalists as the Trichina sjnralis, 

 present in their evolution three well-marked stages of existence for 

 us to stud}', which reall}' anticipate the larva, pupa, and imago phases 

 of development in the winged insects. The natural history of this 

 flesh-worm, therefore, becomes not a little interesting and worthy of 

 special notice in this connection when we endeavor to explain the 

 precise manner of its infection, the phenomena of certain symptoms, 

 and the ultimate cause of death in the human victim. 



The encvsted worm that Owen described is now well known to 

 belminthologists to represent the larval condition of an adult nema- 

 tode. It detracts nothing, however, from the honor of his discov- 

 ery, observes the late Professor Cobbold, that these little worms have 

 turned out to be the wandering brood of a more highh'-organized 

 and dangerous parasite.* 



The body of this flesh- worm is very slender and scarcely visible to 

 the naked eye. It tapers anteriorly, and therefore the head is at the 

 pointed end of the worm. The mouth is round, unarmed and very 

 small. The alimentaiy canal is straight, and is divisible into three 

 distinct parts, corresponding to the oesophagus, stomach, and intes- 

 tines. 



The male is much smaller than the female, as will be seen in com- 

 paring them on the plate, under the same magnifying power. The 

 tail of the male worm is furnished with two lateral appendages, well 

 defined, as seen at Fig. 2. The cloaca situated between these points 

 is reversed during the generative act. 



♦See his classic work on the Entozoa, An Introduction to Helminthology, Lond., 1869, page 

 335. 



