The Growth and Effects of the Tubercle Bacillus on the Chorio-Allantoic Membrane of the Chick Embryo: A Method for Studies in Chemotherapy

Abstract

Four strains of tubercle bacilli including an avirulent H 37 strain from the Saranac Laboratories and a variant H 37 strain from the Phipps Inst. and the virulent human strain A 27 and the bovine Ravenel "smooth" strain also from the Phipps Inst., were cultivated on the chorio-allantoic membrane of the 9-day chick embryo. Tubercles were obtained in 4-6 days after implantation. Membranes inoculated with dead tubercle bacilli and tuberculin gave proliferation of both epithelial and meso-thelial tissue but no tubercles. Normal saline soln. placed on the membranes produced no mesothelial thickening and the slight proliferation which occurred in the epithelial tissue did not appear different from that produced by mechanical injury. A study was made of the incidence of membranes with tubercles and the extent of tubercle development determined by both gross and histopathological methods. The % incidence of membranes with tubercles and the extent of histological change produced can be directly correlated with the known degree of virulence of the strain when injd. into exptl. animals. This method, therefore, is presented as a rapid method for the detn. of the virulence of a strain of tubercle bacilli.