36 Observations on Parasites and Parasitic Diseases 



points of difference between it and the Ptdex irritans consist in 

 the lower part of its head, and the upper and lateral parts of 

 its protothorax being provided with a comb-like fringe. The 

 use of this is not very apparent, but probably by the pectinate 

 edge of the protothorax the creature is enabled to keep a firmer 

 hold of the hairs when travelling over the body of the dog, 

 while by that of the lower part of the head it can the more 

 easily push aside the downy hairs so as to insert its lancets and 

 suctorial organ into the skin to obtain its food. When located 

 on the body, even in small numbers, dog-fleas cause considerable 

 and persistent irritation, but do not give rise to any special 

 form of eruption, although the dog will occasionally rub him- 

 self quite bare in places in his attempt to rid himself of their 

 presence. 



All the metamorphoses which the creature passes through 

 are frequently completed on the skin of the dog, and hence 

 many dogs suffer considerably from fleas for months together. 

 A remarkable instance of this kind was brought under our notice 

 a few years since by Mr. Austin, M.R.C.V.S., of Exeter, in which 

 a dog had been for six months the subject of excessive cutaneous 

 irritation. The case will be found recorded at p. 335 of ' The 

 Veterinai'ian ' for 1855. 



Mr. Austin stated in his communication, that although the 

 itching had existed so long, and was always very considerable, 

 still, when the animal was brought under his care, no eruption 

 was to be observed. On making a close examination, however, 

 he says, " 1 discovered a number of little animals, unlike any I 

 had ever seen before, upon nearly every part of the dog's body. 

 I succeeded in getting some of these alive, mixed, however, with 

 much dirt and scales of cuticle. I send them by a friend, and 

 hope they will reach you before they are dead or dried up." 



In commenting on this case, in the Journal alluded to, we 

 observed, " that more than a month had elapsed before the 

 small jar containing the parasites came to hand, and conse- 

 quently we despaired of finding any of them alive. To our 

 surprise, however, we found three or four still living among 

 the mass of dirt and cuticle. A slight examination Avas sufh- 

 cient to show that these were the larvce of some insect, 

 and the microscope at once decided that they were the 

 larvae of the dog-flea. Further search showed that there were 

 numerous dead larvae and exuvia? present, and therefore, to 

 facilitate our future examination, the whole mass was placed 

 in a phial with some diluted spirit, that the organisms might 

 be freed from the dirt, and be the more readily selected after 

 their imbibition of the fluid. By this means we obtained speci- 

 mens which rendered the history of the dog-flea perfect and com- 



