TRICHINELLID^ 303 



out at the poles, giving them somewhat the shape of a lemon. Their 

 dimensions vary with the thickness of their walls. In general, they 

 are about four-tenths of a millimeter in length by twenty-five one- 

 hundredths of a millimeter in breadth, but their length may be from 

 three-tenths to eight-tenths of a millimeter and their breadth from 

 two-tenths to four-tenths of a millimeter. After the formation of the 

 cysts they are often made more recognizable to the unaided eye by the 

 deposition of fat cells immediately around their poles. Within each 

 cyst there is usually one, more rarely two or more, larvse. 



Tabular Review of Life History of Trichinella Spiralis 



Mature Worms. — In intestines of hog, rat, etc. Period of 

 I intestinal trichinosis. 



Embryos. — In intestinal crypts of same. 



\ 

 Embryos. — In lymph and blood currents after pene- 



I trating intestinal wall. 



Embryos. — Migrating within fibers of voluntary mus- 



I cle. Period of muscular trichinosis. 



Encysted Larvee. — At rest within voluntary muscle- 



I fibers. 



Larvae. — Freed from cysts after ingestion by hog, rat, 



I man, etc. 



Mature Worms. — In intestines of same. 



Degeneration. — After a varying period of time the trichina cyst 

 undergoes fatty and calcareous degeneration. In the first there appear 

 within the cyst cells small fat granules which rapidly increase in number 

 and are soon set free to invade the whole of the cyst. Later there is a 

 deposition of carbonate and phosphate of Hme, the calcification involving 

 the capsule and the tissues of the trichina, though the latter often es- 

 capes the process, and perfectly intact trichinae may be found in cysts 

 entirely calcified and opaque. 



Calcification of the capsule begins about the seventh month after in- 

 fection and is completed in from fifteen to eighteen months, though ex- 

 ceptions give to these periods but a general application. Ostertag 

 states that completely calcified trichina capsules were found in two 

 hogs nine and twelve months old, and, according to the same author, 

 Dammann reported a case in which after eleven years the trichina cap- 

 sules were not completely calcified and contained trichina still capable 

 of producing experimental trichinosis. 



Location. — Encysted trichinae are found in striated muscle in which 

 the fibers have a sarcolemma. They are not found in the muscle- 



