30G PARASITES oi- ANIMALS 



kart succeeded in rearing the sexually-mature DocJimii by 

 introducing the rhabditiform larvse into the stomach of the dog ; 

 moreover, his experiments upon water-snails belonging to the 

 genus Phy$a gave negative results. 



Of Arachnidan parasites (Trachearia) infesting the dog, by 

 far the most interesting is the well-known Pentastoma tanioides, 

 shown by Leuckart to be the adult condition of the still 

 better known Pentastoma denticulatum. It resides in the nasal 

 sinuses. As already mentioned in a former part of this work, 

 these parasites present four marked stages of growth, namely 

 (1), the embryo, (2) the pupa, (3) the active larva (P. denticu- 

 latum), and (4) the sexually-mature worm. As the eggs and their 

 embryonic contents are lodged in the nasal mucus of the dog, 

 and are commonly distributed by the act of sneezing on the part 

 of the animal, the sources of infection are not far to seek. 

 Clearly the larvaB usually get introduced to the bodies of man- 

 kind and herbivorous animals by the ingestion of unclean vege- 

 table matter. The embryos set free in the stomach bore their 

 way to the liver and other viscera, in which organs encystation 

 and moulting subsequently take place. The fondling of dogs 

 infested by pentastomes may prove dangerous by a more direct 

 transference of the eggs to the hands and mouth. As regards 

 the dog, the adult parasite has been known to prove fatal. A 

 very striking instance of this kind was recorded by Prof. Dick, 

 where the worms wandered into the trachea producing asphyxia. 



The ectozoa of the dog, though not numerous as species, are 

 of importance in relation to mange. The follicle-mites form a 

 family by themselves (Demodicidce) , and, as already observed, 

 those infesting the dog and cat are, alike, mere varieties of the 

 human species (Demodex folliculorum, var. caninius and var. cati). 

 Whilst the human parasite restricts itself to the face, the canine 

 variety (fig. 52) will occupy any part of the dog's body. The 

 follicle-mite of the cat, however, usually confines itself to the 

 ear. According to Megnin, to whose beautiful monograph we 

 owe so much, two or three dozen of these parasites may be 

 found occupying a single follicle of the dog. Acne-like pustules 

 are thus formed, and when they are very numerous death may 

 result from the excessive irritation, which is usually accom- 

 panied with depilation. An interesting example of this kind 

 recently occurred at the Royal Veterinary College. In regard 

 to the ordinary mange-mite (Sarcoptes canis, Gerlach) M. Megnin 

 points out that it is in all respects identical with the human 



