644 YETERINAKY HYGIENE 



using youthful vaccinifers, since it is well known that 

 tubercular infection of young stock is of rare occurrence 

 though it is exceedingly common in adults. White and 

 red and white animals are to be preferred to those with 

 black skins, but only with the object of avoiding a dark 

 coloration of the resulting lymph. 



Preparation of the Vaccinifer. — The animal is secured on 

 a tilting table in the position shown in Fig. 190. The 

 upper hind-leg being either held by an assistant, as in the 

 illustration, or secured to a suitable prop fixed to the table. 

 The vaccination area is then shaved, thoroughly cleansed, 

 and dried. 



Vaccination. — The area vaccinated by different operators 

 varies considerably ; whilst some utilize the inside of the 

 thigh, the scrotum, udder, and neighbouring parts, others 

 consider that vesicles in these situations become too 

 advanced, and employ only the more forward parts of the 

 abdomen and sides of the chest. The methods of operation 

 adopted also vary, some scarifying small patches with criss- 

 cross lines, others merely making a series of long or short 

 incisions about f inch apart over the selected area (Fig. 191). 

 Whichever mode be adopted the incisions should be deep 

 enough to admit of a thorough infection, but not so severe 

 as to produce any pronounced bleeding. Into each incision 

 is rubbed a sufficient quantity of a previously prepared 

 vaccine, which should have been stored for a considerable 

 time, and the operation is complete. 



Collection of Li/mp/i.— The lymph is usually collected 

 120 hours (5 days) after vaccination (Fig. 191), and this 

 is generally considered the most suitable time, although 

 3 and 4 day lymph will also give good results, and is some- 

 times utilized. The calf having been secured on the table 

 as before, is again thoroughly cleansed, and the vesicles 

 (incisions) are then scraped with a sharp spoon ; in the case 

 of scarified patches or short incisions, each may be clamped 

 previous to being scraped, but this does not appear to be 

 essential, so long as the deeper portions of the vesicles are 

 secured. The object of the clamping is to cut off the blood 



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