1. That the supply of blood come from a vigorous adult.
2. That the transfer be made within two minutes of the blood’s escape from the vein of the supplier.
3. That, to prevent coagulation, the blood should pass over as small a surface, and suffer as little exposure as possible in transit.
4. Care must be taken to prevent air entering the vein with the blood.
The apparatus described below is that devised by Dr. Graily Hewitt, and depicted in the Obstetrical Society’s Transactions for 1864, page [137]. It consists of a glass syringe holding two ounces (fig. 96), with a piston easily attached and removed; its nozzle is curved and fits the mouth of a cannula of silver. The nozzle of the syringe is provided with a little stopper attached by a chain; a stylet likewise fills the cannula, to be withdrawn when the blood is injected through the latter.
Fig. 96.—Graily Hewitt’s syringe for transfusion of blood.
The success of the operation depends in great measure on the rapidity with which it is performed, and requires the aid of two assistants that the various steps may follow each other as quickly as possible.
Apparatus.—1. Syringe, cannula and stylet.
2. Lancet.