Abstract
Developing chick embryos are now used extensively for the study of viruses and rickettsiae. At present they are used in large numbers for the preparation of vaccines against virus and rickettsial diseases. However, it has always been extremely difficult to sterilize thoroughly the eggshell with ordinary chemical disinfecting agents. In 1939 Penna 1 described a technic in which he employed an oxyacetylene torch for burning the eggshell open while the egg was rotated slowly in an adjustable clamp turned by an electric motor. Penna's technic is satisfactory except that it is too slow. The purpose of this report is to describe a modification of Penna's apparatus which permits a considerably faster removal of embryos under sterile condition.
The apparatus is illustrated in Figs. 1, 2, and 3. The eggs are handled in groups of four carried in shallow metal trays (A). The flame of an oxyacetylene torch (B) is applied at the assumed position of the air sac's margin as each egg is made to rotate through one complete revolution; the optimum rate of turning is dependent on the resistance to burning shown by the shells of a particular lot of eggs, but is usually of the order of 45 rpm. The metal trays serve to retain the embryonic, fluids which occasionally issue forth when a shell cap breaks loose while being flamed. They also perform the same function while the caps are being displaced with a sterile instrument and while the embryos are being removed. The trays and holders can be quickly rinsed in running tap water and then put back into service.
The details of the holders and trays can be seen in Fig. 1. Each holder (C) consists of a 1 5/8- in. length of heavy rubber tubing into one end of which is inserted a 1-in. length of brass tubing (D).
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