70 Ohservafions on Parasites and Parasitic Diseases 



a horse which had been furnished him by my late colleague, Pro- 

 fessor Morton. Kiichenmeister also records that " Oschatz found 

 a similar Acarus in the glands of the eyelids of a sheep. It 

 was, however, broader generally, and especially in front." * 



Besides these instances, we are not aware that the animalcule 

 has yet been met with in any other domesticated animal, ex- 

 cepting the dog, in whom, however, it is not uncommon. In the 

 latter part of 1843 Mr. Topping — a preparer of objects for 

 the microscope — led by the publicity given to this question, 

 sought for the entozoon in^the dog, and found it in great abun- 

 dance. The dog belonged to himself, and had long been the sub- 

 ject of a " pustular affection " of the skin.f Mr. Topping attributed 

 the disease to presence of the animalcules, an opinion which 

 was, however, combated by Mr. Wilson. 



Since 1843 the parasite has been very frequently found in the 

 dog; and in 1849 M, Leblanc, ' Medecin Veterinaire,' Paris, 

 described a disease of this animal ending in marasmus, and de- 

 stroying the dog, in about two months, which he attributed chiefly 

 to the existence of these creatures in immense numbers in the 

 folli'cles of the skin. 



In 1851 we also obtained a large number of these parasites 

 from a dog affected with skin disease, which was accompanied 

 by extensive desquamation of hair and cuticle, and a discharge 

 of a dark-coloured unctuous fluid from the follicles. It was sin- 

 gular, however, that in this instance the dog showed little or no 

 disposition to scratch himself, as is ordinarily the case in skin 

 diseases. We preserved several of the parasites at the time, 

 and give the subjoined illustration of the entozoon from speci- 

 mens still in our possession. 



Compared with the fully developed Aca- 

 rus FoUiculorum of man, the body of that 

 of the dog is scarcely more than half as 

 long. This shorter length, however, does 

 not seem to be due to immaturity, for in all 

 the specimens which we have examined we 

 have not met with a single deviation from 

 this rule. With the exception of this 

 diminished length of body, there is so close 

 an identity in these acari that a description 

 of one applies equally to the other. Accord- 

 Acarus FoUiculorum.— Dog. ing to Erasmus Wilson the acarus of man 

 MaguifieJ. varies in its entire length from l-64th to 



1-1 35th of an inch, and in the length of 



* ' Kiichenmeister,' vol. ii. p. 17. 



t A paper relating to this discovery vras read before the Microscopical Society, 

 Dec. 20th, 1843, by Mr. A. Tulk. See ' Physiological Jourual,' 1843-4, p. 124. 



