DISEASES OF SWINE 541 



therefore, whether pork has been inspected or not, it should be 

 thoroughly cooked or thoroughly cured before it is used for food. 

 -(B. A. I. Cir. 108.) 



Trichinosis is a disease caused by the muscles of the body 

 becoming infested with a very small round worm. The disease is 

 seen in man and other mammals. It occurs in two forms in the 

 one animal; the intestinal, which represents the adult parasite, and 

 the muscular, which represents the larval stage of the parasite. 

 From one to three per cent, of the pork examined contains trichina. 



Description and Life History. The adult T. spiralis is a very 

 small worm. The male a little over one twenty-fifth of an inch 

 long, the female about three times the length of the male. The 

 digestive tract can be divided into a buccal opening, oesophagus, 

 stomach, intestines, anus and cloacal slit. The genital apparatus 

 in the male consists of testicular tube, excretory canal and genital 

 orifice; in the female of ovaries, uterus, vagina and vulva. In- 

 ternal impregnation takes place, and the eggs develop in the uterus 

 of the female to the number of at least a thousand and are born 

 alive. These embryonic worms within a short time after birth pen- 

 etrate through the walls of the intestines and migrate through the 

 tissues until they reach the involuntary muscles. It then enters 

 the muscle fibre, coils itself up and rests. In about two weeks, the 

 cyst can be seen and embryos become transformed into larvae. The 

 tissue in the neighborhood of the embryo, is the seat of cellular 

 infiltration, and the muscles in the region may become swollen, 

 and undergo more or less degenerative changes. Connective tissue 

 forms in the region of the parasite and the cyst containing one or 

 more larvae, is spindle or lemon shaped. The larva is about one 

 twenty-fifth of an inch in length. The formation of the embryos 

 begin about the seventh day after the cysts are taken into the 

 digestive tract. The emigrating period is prolonged to the second 

 or third week, and the encysting period from the fourth week to 

 the third month. After the third month degenerative changes 

 begin in the cyst and finally involve the larvae as well, but these 

 changes (calcareous degeneration) may take place very slowly and 

 not occur for a year or more. When the cyst does become calci- 

 fied, danger to the infested individual is over. One ounce of the 

 flesh of an infested pig may contain eighty-five thousand encysted 

 worms. 



Method of Infection. Infection occurs from eating flesh con- 

 taining the live larvae of the T. spiralis. The source of the infec- 

 tion in swine is from eating rats. According to the investigations 

 made by Stiles, rats around the country slaughter houses are quite 

 generally infested with trichina, as it is rare to find the offal in 

 country disposed of in the proper way, and rats are abundant 

 around such places. Hogs frequently have the same opportunity, 

 as the rats to feed on offal and under such conditions infection may 

 occur. 



Symptoms. These have been observed in experimental ani- 

 mals and in man. When only a few embryos migrate through 



