198 



PARASITES OF THE DOMESTIC ANIMALS 



Fig. 107. — Diagram 

 Cystioercus. 



7 by 4.5 mm* (9/32 by 3/16 of an inch), while those of the bladder were 

 6 by 4 mm. (1/4 by 3/16 of an inch). 



Degeneration. — After a period of time, depending somewhat upon 

 their location, the cysticerci undergo caseous degeneration followed by 

 calcareous infiltration. That these changes may 

 set in early has been shown in the experiments 

 of Hertwig, who found them four weeks after 

 infestation. Commonly the degenerative changes 

 do not occur until full development is reached or 

 for some time after. The cysticerci most likely 

 to undergo early degeneration are those located 

 in the heart, while those of the muscles of 

 mastication probably survive the longest. If 

 they are found degenerated in the latter muscles, 

 therefore, it is not hkely that cysticerci in other 

 parts of the body will be living unless they are from a later infection. 

 The degenerated cysts may be recognized by their yellowish, or some- 

 times greenish color. They may be semisohd or quite gritty; pus may 



be present as a result of pyogenic or- 

 g-anisms gathered by the embryos in 

 their migrations. The caseation, how- 

 ever, may not always involve the para- 

 site. In such cases the scolex is likely 

 to be found just under the cyst wall with 

 its usual characteristics retained, though 

 the caudal bladder is apparently absent. 

 As cysts when dissected away and ex- 

 posed to the air tend to shrink by evapo- 

 ration, their structure is more easily 

 made out if they are kept , moistened 

 with a drop or two of water during the 

 examination. 



Vitality. — The cysts of beef measles 

 naturally disintegrate at about three 

 weeks after the death of the host, there- 

 fore meat kept in cold storage for this 

 period will not be likely to contain livirig 

 larvse. In fresh beef all will be killed 

 by the application of sufficient heat (fiO- 

 70° C. = 140-156 F.) to cook the meat 

 until its cut surface presents a uniform gray color throughout. Freezing 

 for a number of days will destroy them, but this method has a disad- 

 vantage in that decomposition of the meat follows rapidly, making it 

 necessary that it be quickly used. Based upon experiments by Ran- 



FiG. 108. — ^Fragmeut of beef mus- 

 cle, showing cysts of Cysticercus 

 bovis, — natural size (after Neveu- 

 Lemaire, from Railliet). 



