CHAPTER VH 



INOCULATION. 



By inoculation is meant the intentional conveyance of infectious 

 material to a healthy subject. A wider meaning is sometimes attached 

 to the term, causing it to extend to the products of micro-organisms 

 such as antitetanic and antidiphtheritic serum, mallein, etc. The 

 reasons for inoculation vary. At the present day inoculation is a most 

 important process in studying the life history of bacteria, their nature, 

 virulence, mode of action, etc. Animals, again, are inoculated to 

 protect them against certain diseases, like pleuro-pneumonia contagiosa, 

 black-quarter, anthrax, and swine plague (rouget du pore), to produce 

 new (modified) infectious material (vaccine), and finally, though not 

 very often, to shorten the duration of epizootic diseases. Various 

 forms of needle are used for inoculation. The oldest is Sick's (Fig. 138). 

 A longitudinal furrow in the middle of the head holds the infective 

 material. From the centre of the lancet-shaped head the sharp 

 cutting borders converge to form a fine point. 



Fig. 139 represents Pessina's needle. In use the furrow is filled 

 with infectious material, the needle thrust under the skin, revolved 

 and withdrawn, leaving the infective material within the wound. 

 Inoculation may also be performed by first slightly scarifying, reall\' 

 only irritating the skin, and then rubbing in the infective material. To 

 produce a large number of incisions at one stroke a special compound 

 spring scarifier has been made, though it is not indispensable. 



Sticker employs a special needle (Fig. 140) for pleuro-pneumonia 

 inoculations. It consists of a hollow needle provided with a small 

 opening just below the slightly curved point. The handle has a 

 movable pressure button, which injects a small quantity of fluid into 



