182 THE CANADIAN NATURALIST. [June 



shows two generations on or near the same line of muscle. 

 The faint curve near the edge of the margin being a larger 

 and older worm than the other three, it is but partially in 

 focus, and only about one half is, therefore, seen. 



These worms have been generally figured in works on 

 Physiology in two conditions, viz., encysted in the muscle, 

 and sexually developed in the intestinal canal. The appearance 

 of the young sexless worm in transitu in the flesh has not 

 been carefully described. Some observers have, therefore, 

 mistaken it for another species, whilst others have overlooked 

 it altogether. The photographs Nos. 1, 3, 4 and 5 show 

 fairly the varied forms in which the worm may be . expected 

 to be found in flesh during periods of from one to six weeks 

 after ingestion. After a period of from six to twelve months 

 the cysts become covered with a phosphatic opaque deposit, 

 and the worm can only be seen by dissection or by solution 

 of the coating in weak acid. These old cysts are sometimes 

 found empty. 



The best medium which I have found for mounting recent 

 muscle for the examination and extraction of specimens, under 

 the microscope, is a mixture of one part glycerine and one part 

 aqueous carbolic acid. The muscle may be conveniently 

 examined by a two- third object glass, and a B. or C. eye 

 piece with the smallest aperture in the diaphragm. The 

 extracted worm is best seen under a ^inch objective, with a 

 small pencil of light, or by polarised light. No. 1 is magnified 

 100 diameters; Nos. 2 and 3, 150 diameters; Nos. 4 and 5, 

 50 diameters. 



In 1866 some valuable experiments were conducted, in 

 reference to the propagation of these worms, by Dr. T. Spencer 

 Cobbold,* whose researches on Cestoid Entozoa place him at 

 the head of English authorities on such subjects. 



After feeding animals with trichinous food, seven experiments 

 on birds all proved negative. Three sheep, two dogs, one 

 pig and one mouse gave also negative results. 



Nine cases were successful, viz., four dogs, two cats, one 

 pig, one Guinea pig and one hedgehog. 



While we may, therefore, conclude that birds and herbivorous 

 mammals are very unlikely subjects for infection by this 



JourQal of the Linnean Society, Zoology, vol. 9, p. 205. 



