DISEASES DUE TO EPIZOA. 723 



galleries beneath, the epidermis, and it is very possible that all 

 are not reached by the dressing until the animal has been 

 dressed three or four times. 



Smearing sheep with greasy ointments, or dressing them 

 extensively with oil of tar or mercurial ointment, is a very 

 dangerous practice, and often causes many deaths. They prove 

 injurious to the animal by clogging the wool and rendering the 

 skin impervous, thus preventing the cutaneous exhalations, and 

 causing the accumulation of effete materials in the blood — car- 

 bonic acid, ammonia, and other organic products — which are 

 naturally thrown off through the pores of the skin. The 

 symptoms of the disease so produced are hurried breathing, 

 small, frequent pulse, blood-shot eyes, and a discharge of frothy 

 mucus from the nose and mouth. The post mortem appearances 

 are congestion of the lungs, the trachea and bronchii filled with 

 mucus, and the great veins filled with a dark-coloured semi- 

 coagulated blood. 



In mercurial poisoning the symptoms are those of insalivation, 

 purging, redness of the skin, foetor of the breath, and rapid 

 sinking. 



Treatment. — The animals must be clipped and thoroughly 

 washed with soap and water. They must be supported by stimu- 

 lants, such as wine, whisky, or other spirituous liquors, after- 

 wards treated with great care, and have good food and warm 

 shelter. 



DISEASES DUE TO EPIZOA. 

 The second class of parasites that infest the skin of the lower 

 animals consists of insects which live upon the skin. 



LICE, 



(Pcdiculidce, class inscda, division articulata, and order anoplmra), 

 are parasites destitute of wings, hatched from eggs, undergoing 

 no transformation in the process of their development, but shed- 

 ding their skins a certain number of times. The state of lousi- 

 ness is termed phthiriasis, and is seen in poor, half-starved, or 

 very old animals. The best treatment is clipping, if the hair be 

 long, washing the animal with a decoction of stavesacre, one 

 ounce of the powdered seeds to a pint of weter, and taking care 



