180 



EXPERIMENTAL INOCULATIONS 



distance of from a few millimetres to 2 cm. according to the species of animal 

 used, the operator can feel that it is moving freely in a cavity. At this stage 

 the fluid is inoculated. 



4. Withdraw the needle quickly. Stitch up the skin and paint the wound 

 with collodion. 



E. Inhalation. 1. Put the animal in a solid- walled metal cage having 

 an observation window on one side and on the other two holes lightly plugged 



with cotton- wool to allow of interchange of air : 

 the tube from the pulverizer passes through a 

 third hole. 



2. Liquid cultures may be pulverized by means 

 of Richardson's apparatus, but when the virus 

 can be used dry without losing its virulence it 

 is better to pour the liquid culture on to lyco- 

 perdon spores, lycopodium powder, or on to wood 

 charcoal reduced to an impalpable powder. The 

 culture is intimately mixed with the powder and 

 then dried in vacuo over concentrated sulphuric 

 acid. The powder well dried is then pulverized 

 in the cage with a pair of bellows. 



Note. When dealing with micro-organisms patho- 

 genic for man, the operator should be particularly 

 careful to protect himself from the dust, and the 

 experiment should be done, for choice, in the open 

 air. 



(xiv) Intra-cranial inoculation. 



Intra-cranial inoculation is generally performed 

 on the dog, guinea-pig or rabbit. 



A. 1. Fasten the animal on its belly, the head 

 being firmly held by an assistant. 



2. Shave" and cleanse the scalp behind the 

 orbits. 



3. Make an incision through the skin and 

 aponeurosis about 3 cm. long in the middle line, 

 commencing at a point level with the upper 

 borders of the orbits. Retract the edges of the 

 incision with a speculum. In the dog the incision 

 is made preferably a few millimetres from the 

 middle line to avoid the superior longitudinal 

 sinus. 



4. Place a small trephine about 5 millimetres 

 in diameter (fig. 142) on the skull towards the 

 middle of the incision and a little outside the 

 middle line. 



Commence trephining and when the teeth bite 

 raise the axis to prevent wounding the brain. 



Ascertain frequently to what depth the trephine has reached and when 

 resistance has ceased raise the circle of bone with a pair of forceps or small 

 elevator. 



5. The dura mater is now visible at the bottom of the wound. Pass the 

 needle very obliquely through the meninges so that the brain may not be 

 injured, and inject the fluid. It is well to use a needle bent to a right angle 

 at the middle point of its length. 



FIG. 142. Trephine for small 

 animals. 



