INTRA-SPINAL INOCULATION 181 



6. Withdraw the needle, touch the puncture with a sponge soaked in 

 carbolic water, suture the skin and apply collodion to the incision. 



B. In injecting small doses of toxin into the cerebral tissues the foregoing 

 technique may be simplified. 



After shaving, cleansing and incising the skin make a small hole in the 

 skull with a drill, limiting the depth of the perforation with a shield to 

 avoid damaging the meninges. Then the needle is introduced to the 

 required depth (determined beforehand by means of a probe) the toxin 

 injected, the puncture touched with carbolic and a stitch put through the 

 skin and covered with collodion. 



(xv) Intra-spinal inoculation. 



Intra-spinal inoculation is effected through the posterior occipito-atloid 

 ligament. With a little practice it is easy to inoculate directly into the spinal 

 canal of a rabbit or dog by forcing a curved needle into the ligament through 

 the skin (which must have been previously cleansed) : the needle passes 

 behind the posterior occipital tuberosity just outside the middle line and 

 is then turned and made to follow the occipital bone. Before injecting 

 make sure that the needle has passed well into the canal by aspirating a 

 little of the cerebro-spinal fluid into the syringe (which should be not quite 

 full of the material to be injected). The inoculation must be done very 

 slowly. 



It is easier, especially in the guinea-pig, to fix the animal on its belly with the 

 head flexed, j:hen to divide the posterior cervical muscles transversely on a very 

 small director below the posterior occipital tuberosity, avoiding the vertebral veins. 

 When the muscles are divided the ligament will be seen and will be recognized 

 by its pearly- white appearance. Bleeding is easily arrested by plugging the wound 

 with wool soaked in a solution of peroxide of hydrogen. By keeping close to the 

 lower surface of the occipital bone the membrane is easily pierced with a curved 

 needle. After inoculating insert two sets of sutures and paint the wound with 

 collodion. 



(xvi) Inoculation into the alimentary canal. 



A. Ingestion. (a) The simplest method is to mix the culture with the 

 animal's food, viz. bran in the case of rabbits and guinea-pigs and meal in 

 the case of dogs. 



(b) In small animals the culture may be sucked up into a Pasteur pipette 

 which is then introduced into the animal's mouth, and the liquid allowed to 

 fall drop by drop while the head is held up. The end of the pipette should 

 be short and stout. 



[In the experiments of the Royal Commission on Tuberculosis (1901) it was found that 

 pipette-feeding experiments with liquids were unsatisfactory. The animal may cough 

 or choke, and the fluid find its way to the lungs. Even when the fluid appeared to be 

 swallowed quite satisfactorily disease of the lungs was sometimes found which could 

 not have been of intestinal origin. Experiments conducted on these lines are likely, 

 therefore, to lead to erroneous conclusions.] 



(c) In the case of birds make small pellets of flour and mix the 

 culture with it. Put a pellet on the base of the tongue and close the 

 beak. 



B. Oesophageal catheterization. This method is more certain than the 

 foregoing and moreover the amount of liquid injected can be measured. 



Guinea-pigs and rabbits. The animal with the head moderately extended 

 is held by an assistant. By pressing the cheeks near the molar teeth the 

 mouth can be opened and a small gag with a hole in the centre, or, better, a 

 piece of iron wire bent into a rectangle, can be placed between the jaws behind 



