196 



THE COLLECTION OF MATERIAL 



Collection of serum. 



On account of the importance at present attaching to a study of 

 serum reactions it is often necessary to collect serum from immunized 

 animals. 1 In the case of large animals it is best to bleed by the method 

 described on p. 49. Small animals may be bled preferably from the carotid 

 by the method just described, and after the clot has contracted the serum 

 can be decanted. But by this method much of the serum 

 is lost, being retained in the meshes of the clot and it is 

 better, therefore, when the amount of blood available is 

 strictly limited as is the case with small animals, to bleed 

 into a Latapie's tube. By using this apparatus all chance 

 of contaminating the blood is avoided and a yield of 80 per 

 cent, of the- total volume of serum is assured. 



Latapie's apparatus. This (fig. 148) consists of a large glass 

 tube B constricted about its lower third E, and having a small 

 cup F at its lower end. Below the constriction there are two 

 tubulures, one T, straight and open and plugged with wool between 

 two constrictions ; the other D, on the opposite side, bent in the 

 form of an inverted U, and drawn out at its free end to a fine 

 point which is sealed. The upper end of the large tube B is 

 connected by means of a piece of india-rubber tubing with another 

 tube A, known as the trocar tube, consisting of an ordinary test- 

 tube bent in the form of a right angle and drawn out to a fine point 

 at its free end. This second tube A passes well down into the 

 larger tube B, leaving the bent and pointed end projecting. 

 Occupying the centre of the apparatus from top to bottom is a 

 small glass tube H, sealed at one end and the sides perforated with 

 numerous holes. 



Technique. Place a few drops of water in the apparatus and 

 sterilize it in the autoclave at 120 C. Ex- 

 pose the carotid in the ordinary way then 



break off the point of the tube A with a pair of sterile forceps 



and pass it into the vessel, holding the apparatus so that the 



broken point is downwards. Blood will now ascend into the 



tube A. Stop the flow of blood before the latter is quite full, 



then seal the pointed end of A in the flame, gently aspirating 



through T to prevent the blood being clotted by the heat. 



Stand the apparatus on one side with the tube A downwards. 



The clot forms around the narrow central tube H, and re- 



tracts from the walls of A. If the apparatus be now inverted 



the serum will fall into the collecting bulb R, the red cells 



precipitating into the cup F. In this way 80 per cent, of the 



serum can be collected in a few hours, and can be easily with- 



drawn through the tubulure D by breaking its point and 



blowing through T. With a little experience and skill a small 



animal such as a rabbit or guinea-pig can be bled two or three 



times without killing it. 



Stassano's apparatus. Stassano's apparatus is somewhat 



similar to Latapie's but is fragile and more expensive. 



Lumiere's tube. This consists of a glass tube (fig. 149) on 



which two bulbs B and D are blown, the interior of the lower 



B having a number of projecting points. The tube is plugged 



with wool at the ends and sterilized in the hot air sterilizer. 



To use the apparatus the tube A is fitted with a short piece 



of india-rubber tubing carrying a sterilized platinum-iridium 



syringe needle. As soon as the vessel is penetrated, blood 



will flow into the bulb B. When the latter is full, the tubing 



is pinched and the needle withdrawn from the vessel. The 



1 The collection of serum for use as a culture medium is described in Chapter II. 



FIG. 148. La- 

 tapie's apparatus 

 for collecting blood 

 from small animals . 





