238 



THE TAPEWORMS 



in an experiment to test the penetration of heat, a ham cooked 

 by boihng for two hours had reached a temperature of only 

 115° in the center. When roasted, pork should always be cut 

 into pieces weighing no more than three or four pounds to insure 

 thorough penetration of heat. Beef which has lost its red or 

 " rare " color is quite safe. 



Since bladdcrworms are unable to survive the death of their 

 host for more than a limited time, they are eventually destroyed 

 bj' ordinary cold storage — within three weeks in the case of the 

 beef bladderworm, Cysticercus hovis, but not always so soon in 

 the case of the pork bladderworm, C. cellulosce. According to 

 Dr. Ransom temperatures of about 15° F. kill beef bladder- 

 worms within five days. Thorough curing or salting of meat is 

 also destructive to the parasites. 



Infected persons should be careful not to contaminate the 

 food or water of domestic animals with their faeces, bearing in 



Fig. 87. Heads of some adult tapeworms found in man, drawn to scale; A, 

 beef tapeworm, Taenia saginala; B, pork tapeworm, T. nolium; C, fish tapeworm, 

 Dibothriocephalus latus; D, heart-headed tapeworm, Dibothriocephalus cordatus; 

 E, African tapeworm, T. africnna; F, double-pored dog tapeworm, Dipylidium 

 caninum; G, dwarf tapeworm, H ymenole pis nana; H, rat tapeworm, HymenoUpia 

 diminuta. X 10. 



mind the various ways in which the eggs may be disseminated 

 — by streams, rain, flies, etc. 



The eggs of the dwarf tapeworm, Hymenolepis nana, are 

 thought to be able to develop through the bladtlerworm stage 

 to the adult in a single host, and should therefore be guarded 

 against by different measures (see p. 243). The larvae of other 

 species of Hymenole-pia develop in insect larvae such as mealworms, 

 and are therefore subject to still different means of prevention. 



The tapeworms of man belong to two quite distinct families, 

 the Tacniida), in which the scolex is rounded and furnished witli 

 four cup-shaped suckers (Fig. 87, A, B, E, F, G and H), and the 



