5TSEASES OF THE SKIN. 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 provBi 

 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 

 S)-mptoms of the disease so produced are hurried breathing, 

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

 mucus from the nose and mouth. The jpost tnortcm appearances 

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

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

 coagulated blood. 



In mercurial poisoning the symptom** are those of insahvation, 

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

 ainking. 



Treahnent. — The animals must be cli2)pod and thoroughly 

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

 lants, suoh 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 lowei/ 

 Animals consists of insects which live upon the skiiu 



LICE, 



{Pediculida, class insecicL, division ariiculata, and order anopJiiira), 

 are parasites destitute of wings, hatched from eggs, undergoing 

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

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

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

 Tery old animals. The best treatment is clipping, if the hair bo 

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

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



