CATTLE. 329 



Medical Science as born on the three hundred thirty-sixth day. 

 It is the general observation that in the majority of prolonged pregnan- 

 cies the offspring is male. Lord Spencer found a preponderance of 

 males between the two hundred ninetieth and the three hundreth 

 days, but strangely enough all born after the three hundredth day under 

 his observation were females. It might be reasonably inferred that while 

 the prevailing tendency is to carry the males overtime, yet that the 

 smaller and comparatively much less developed female sometimes fails 

 to stimulate the womb to contraction until very far beyond the regular 

 date. 



DISEASES OF THE SKIN CAUSED BY PARASITES. 



Mange or Itch. This is a disease of a local nature, due to a mite, 

 which induces irritation and incrustation on the surface of the body gen- 

 erally. It is always contagious, requiring for its development the trans- 

 plantation of the parasites or their eggs from the diseased to the healthy 

 animal. This disease is not very common among cattle in this country, 

 while in some countries it prevails as an epizootic. Poor hygiene seems 

 to favor the extension of the disease, and it is claimed that weakened 

 cattle are more predisposed to harbor the parasite than strong, healthy 

 ones. It is also more prevalent in winter than in summer, and in the 

 latter season sometimes entirely disappears. 



Cattle are afflicted with two varieties of these parasites. They belong 

 to the class (Arachnidae); genera, [Psoroptes (Dermatodectes)] which 

 simply bite and hold on to the skin; and [Chorioptes (symbiotes)] liv- 

 ing together in large families, and not piercing further than the cuticle 

 in search of food. 



Dermatodectes communis, is the most frequent one met in cattle. It 

 lives on the surface of the skin, and gives rise to much irritation by bit- 

 ing. It generally chooses the regions of the the shoulder and root of 

 the tail for its habitation. From these localities it gradually extends by 

 increase in numbers, causing intense itching and great distress in the 

 affected animal. From the irritation of the skin papular nodules appear, 

 which develop into vesicles filled with fluid aud rupture. The drying 

 of the exuding fluid forms crusts, and these are liable to be followed by 

 ulceration. The hairs may project up through the crust or fall out. 

 In chronic cases the skin becomes thickened and almost insensible, dry, 

 and wrinkled. As it is easy to confound this disease with eczema, our 



