42 THE HISTOIIY, NATURE, SYMPTOMS, AND 



lymph, wliicli is best obtained from pustules from a previous 

 iuoculation, and taken from young animals. The best lymph 

 is a transparent fluid, with a slightly reddish tint. The best 

 seasons for inoculating are spring and autumn, when it is neither 

 too cold nor too hot. Having made due preparations, then, take 

 a small lancet and make an incision between the epidermis and 

 true skin on any convenient part of the body bared of w^ool, 

 frequently in the ear or tail, then charge an ivory point, shaped 

 like an arrow, with the lymph, and insert it in the incision made 

 for a few minutes, using slight pressure in withdrawing the 

 point, to ensure its being deprived of the variolous lymph. 



It is of the utmost importance to be able to distinguish the 

 symptoms of this malady from those of the other eruptive ovine 

 diseases. Ovine scabies or sheep scab exhibit certain character- 

 istic symptoms resembling smallpox. They are both eruptive 

 diseases of the skin ; but though the general features resemble 

 each other, the two diseases are, nevertheless, quite distinct 

 and different. The period of latency in smallpox varies from 

 five to twelve days ; in that of scab from ten to twenty-five 

 days. There is neither loss of appetite, nor fever, nor dulness, 

 nor increase of temperature in scab previous to the eruption. 

 The earliest symptom is itchiness of the skin, the sheep fre- 

 quently rubbing itself against posts, gates, fences, trees, &c., 

 twisting the head, and nibbling amongst the wool. After the 

 disease is fairly established, tufts of wool are pulled out by their 

 teeth, thus causing the ragged appearance the wool then pre- 

 sents. When a considerable part of the body is affected,' the 

 animal becomes very uneasy, and frequently attempts to scratch 

 the affected part with its hind foot. If we rub. the skin with 

 the hand, it seems to exhibit delight, stretching the head and 

 neck, moving the lips and jaw^s, and attempting to scratch those 

 who in some decree lessen the acuteness and continuance of the 

 irritation. 



The situation of sheep-pox differs from that of scab. In 

 the former it has been shown that the favourite seats of erup- 

 tion are those where the skin has a hairy instead of a woolly 

 covering; but scab is developed on those parts of the body 

 where the wool is thickest, as the neck, shoulders, and back, 

 where the acari can be well sheltered. After the parasite has 

 deposited itself, a little vesicle is soon developed, containing a 

 reddish yellow serous fluid. When the contents of this vesicle 

 are discharged, a crust or scab is formed of the same colour. 

 On the border of this crust the parasites multiply with remark- 

 able rapidity. The vesicles in scab become confluent ; they 

 form more rapidly, and burst without degenerating into pustules 

 as in sheep-pox. The symptoms, which are of special import- 

 ance, are mainly two in each disease, and these show the clear 



