THE respiratory tract of the developing chick embryo is susceptible to infection with various bacteria and the viruses of influenza, psittacosis, herpes and certain other infections of man and animals. This infection of the respiratory system is secured most readily by an inoculation of the virus directly into the amniotic cavity. Various techniques have been devised for this purpose, by Goodpasture, Hirst and others, but the most popular is probably that of Burnet1. By this method, virus is inoculated under direct vision into the amniotic cavity, which seems preferable to methods where the inoculation is made ‘blind’.