RARITY OF THE BLADDER- WORM. 471 



of the associated tape-worm, only became known when its existence 

 was proved by my experiments. This is explained, however, when 

 we take into account the habits of the ox, and consider that it is 

 not only kept clean and carefully tended, but that, being entirely 

 a herbivorous animal, it has seldom opportunity to swallow large 

 masses of worms with the food which it takes in the open air. It 

 will, therefore, usually pick up only single proglottides, and, as we 

 learn from the result of Zenker's experiment, this would furnish, as 

 a rule, only few bladder-worms. The parasites are, moreover, distri- 

 buted over a large mass of flesh, so that they only occur separately, 

 and may be all the more easily overlooked, since, even in their adult 

 state, they are hardly ever larger than a pea. 



But even since the discovery of the bladder-worms they have but 

 rarely come within the range of observation, at least in Germany and 

 the neighbouring countries. Siedamgrotzky once found one in Zurich, 

 in the muscle of the lip of a living ox; 1 and Gloss, in Frankfort, 

 proved its presence in a tongue, which (according to Heller) is still 

 preserved, partly in the collection of the Senkenberg Institute, and 

 partly in the Pathological Institution at Kiel. Guillebeau 2 has also 

 lately found another instance of the occurrence of the bladder-worm 

 in the tongue of an ox. 



In other districts, bladder-worms from the muscle of the ox have 

 been more frequently observed. We learn, for example, from Knoch 3 

 that the St. Petersburg sausage manufacturers have long known them, 

 and that they describe them, in contrast to the pig bladder-worms, as 

 " dry, hard, and not so watery" a description which is in complete 

 harmony with the smaller size of the bladder, and the accumulation 

 of the " cheesy " enveloping substance. Knoch himself first observed 

 the bladder- worms in a cutlet, which came to table cooked, and it was 

 afterwards established, by his investigations, that the flesh of the cow 

 in question, which came from the neighbourhood of St. Petersburg, 

 was everywhere infested with cysts "of a dirty white colour, or 

 inclining to yellow." 4 According to the assurance of the vendor, the 

 newly cut meat had been inspected by the police medical inspector, 

 and pronounced faultless. As we are informed in the description, the 

 bladder- worms were, moreover, in very different stages ; for while some 

 were quite full grown, others had not even the rudiments of a head, 

 so that we are justified in concluding that there had been a repeated 



1 Bericht d. naturf. Gesellsch. zu Zurich, Dec. 1869. 



2 Mitth. nat. Gesellsch. Bern, p. 21, 1879. 



3 St. Petersburg Medical Gazette, vol. x., p. 245, 1866 (Russian.) 



* Hull. Acad. impe'r. St. Peter sbourg, t. xii., p. 347, 1867. While attempting to give 

 these opinions prominence rather than my own, I must say that there are many state- 

 ments and representations in the course of the essay which I am forced to reiect. 



