Diseases of the Respiratory Organs. 35 



changing it and also to the general sanitary condition of 

 the place. The disease broke out, too, during a spell of very 

 severe weather, when the food left in the pans froze quickly. 

 The course of the epidemic was short, lasting between six 

 and seven weeks, a sufficient time, however, to destroy 

 almost all the pups in the kennels. 



" The mode of invasion in parasitic disease of the bron- 

 chial tubes has been, and still is, a matter of much dispute, 

 some observers maintaining that ' the ova and young para- 

 sites taken up with the food in the first place gain access 

 from the alimentary canal to the circulation ; ' others hold 

 the view that they pass directly from the mouth to the 

 trachea, or that the ova are inhaled by the breath. The 

 former view is the one most generally entertained, and it 

 is urged in its favour that the presence of the worms has 

 been determined in the cavities of the heart and in the 

 blood-vessels, as well as in the intestines. Now, in the 

 epidemic under consideration, I think this view does not 

 meet the case. Supposing the young embryos to have been 

 ingested and to have gained access to the branches of the 

 portal vein, they would then be carried to the right side of 

 the heart, and from thence to the lungs, by the pulmonary 

 artery, the capillaries of which ramify in the lung-substance 

 alone, a situation in which the parasites did not occur. To 

 get to the bronchial mucous membrane they must be re- 

 turned by the pulmonary veins to the left side of the heart, 

 enter the aorta, and pass out by the small bronchial arteries 

 which supply the tubes — an exceeding roundabout and some- 

 what improbable route. It is to be remembered that young 

 strongyles have been found capable, like many other nema- 

 toid worms, of reviving on the application of moisture after 

 a desiccation of a month or more, and even after immersion 

 in spirits of wine and solutions of corrosive sublimate and 

 alum (Williams), so that their chance of survival under 

 adverse circumstances is unusually good. It seems 

 quite as reasonable to suppose that the dried em- 



D 



