202 



ENTOZOA FOUND IN MAN. 



being uncommon, that during the last five years, 

 evidence of the attacks of this entozoon have been 

 remarked in 2 per cent, of the subjects dissected in 

 the Anatomy Rooms of the University of Edin- 

 burgh. 



The trichina is a nematoid worm, about s^th of 

 an inch in length, and y^o^h of an inch in diameter. 

 It is always enclosed in a cyst, of which the long axis 

 lies between, and parallel to the direction of, the 

 fibres of the muscle ; about one -third of this cyst is 

 occupied by the entozoon, which is rolled up spirally, 

 forming two or three spiral turns, whence the name 

 given to it by Professor Owen is partly derived. It is 

 usually solitary, although in some rare instances two, 

 Tiix- 14.' and sometimes even 



three, trichinae have been 

 found within one cyst. 



The cyst is generally 

 an ovoid vesicle pre- 

 senting a prolongation 

 at one, or both, of its 

 extremities, so that it 

 has a spindle-shaped ap- 

 pearance. The dimen- 

 sions of the cyst are very 

 variable, as is also the 

 thickness of its walls. 

 Accordmg to Owen, and 

 most other observers, it 



^ Fig. 14. — 1. A portion of the biceps muscle of the arm, 

 iiitudded with the cysts of the Trichina spiralis. 2. A single cyst. 

 3. A cyst magnified twenty times, and containing calcareous 

 matter. 4. A cyst containing two worms. 5. A trichina mag- 

 nified two hundred times ; a, the head ; b, the tail. 



