FORMATION OF CYSTS 



291 



When the larvse have arrived at their destination in the muscles 

 they thread their way between the fibers towards the ends of the 

 muscles (Fig. 120), ultimately penetrating the individual fibers 

 where they coil up into loose spirals, constantly coiling and un- 

 coiling as much as their close quarters will permit. When worms 

 which are still boring are teased out of the flesh and warmed to 

 blood heat, they can be seen constantly tightening and loosening 

 their coiled form, reminding one of a fist being alternately clenched 

 and unclenched. After entering muscle fibers the worms grow 

 rapidly in size to a length of one mm. (gV of an inch), ten times their 

 original size, and become sexually differentiated. The inflam- 

 mation caused by the movements and waste products of the 

 animals results in the degeneration of the enclosing muscle fibers 

 and in the formation, beginning about a month after infection, 

 of connective tissue cysts around the young worms. The cysts 

 (Fig. 118), which are completely developed in from seven to nine 

 weeks, are lemon-shaped, from 0.25 to 0.5 mm. (y^o to i^ of an 

 inch) long, lying parallel with the muscle fibers. As a rule only 

 one or two worms are enclosed in a cyst but as many as seven in 

 a cyst have been observed. When first formed the cysts are 

 very delicate and can only 

 be seen by careful focusing 

 with the microscope, but 

 they gradually grow thicker 

 and more conspicuous, and 

 after seven or eight months 

 there begins a deposit of 

 chalky calcareous matter 

 (Fig. 121 A). This process 

 ultimately results in the 

 entire cyst becoming hard- 

 ened into a calcareous 

 nodule (Figs. 121B and C), and even the enclosed worm, 

 which usually degenerates and dies after some months, becomes 

 calcified after a number of years. There are cases, however, 

 where the trichina worms do not die and disintegrate so soon, and 

 the calcification process is much slower. There are records of 

 these worms found living in cysts in hogs 11 years after in- 

 fection and in man 25 to 31 years after, though it is doubt- 

 ful whether in some of these cases a fresh infection did not 



Fig. 121. Stages in calcification of trichina; 

 A, ends calcified; B, thin layer of calcareous 

 material over whole cyst, worm beginning to 

 degenerate; C, complete calcification. (After 

 Ostertag.) 



