June] EDWARDS — ON TRICHINA SPIRALIS. 181 



and Zenker the period of incubation of the cyst in the stomach 

 is from six to eight days. This has been erroneously inter- 

 preted to mean that such a period must elapse before any 

 marked symptoms can be recognized. Such a period of time 

 however, is meant to be inclusive of the reproducing power 

 of each individual, from whose body successive broods of young, 

 numbering from 100 to 200, are discharged. Dr. T. S. 

 Cobbold* has found a period of sixty-nine hours amply sujBBcient 

 for the development of the young muscle flesh worms of the 

 human subject into the sexually mature adult Trichina of 

 the dog. If all the worms were calcareously encysted a 

 delay of from three to six days might be expected before 

 intestinal irritation was a marked symptom. But in cases 

 where the worms are young and free in the muscle, develop- 

 ment may take place in a few hours, and rapid multiplication 

 take place before other encysted worms were released from 

 their capsules. 



Thus a succession of fresh irritations to the muscular and 

 nervous system may be expected from the first few hours to 

 a period of eight or ten weeks. In the fatal cases examined 

 in Chicago and Hamilton no single case of encysted Trichina 

 was found in the flesh, but in the Montreal cases one or two 

 distinct and complete cysts were extracted from the man's leg. 

 This was eight weeks after eating the pork, and when the 

 symptoms had somewhat abated, but considerable pain still 

 felt in the muscles. The great shock to the system, which 

 frequently terminates fatally, appears to result from excessive 

 generation of the worms at any one period; — thus young and 

 healthy persons are frequently killed sooner than older and 

 more feeble individuals, the reason being that in the former 

 case probably more food is eaten, digestion is more rapid, 

 nausea more readily overcome by active exertion, and the 

 breeding of the worms becomes excessive and continuous. In 

 the Hamilton cases the young woman died in three weeks, 

 whilst her mother survived six weeks, after eating the fatal 

 repast. Nos. 2 and 3 in the photograph show examples of 

 the worms in the latter case. In No. 2 the worm is carefully 

 picked out from the muscle. No. 3 shows the muscle containing 

 the worms in various postures on a line of muscle, it also 



* Journal Linnean Society, vol. ix, page 209. 



