32 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



again to the original status of the problem. It was decided 

 to test out various bacteriological culture media and to 

 devise new media. 



Experiments were then made in which liver tissue from 

 fetal and new-born rabbits was planted in a number of the 

 more commonly used culture media. The results of these 

 experiments were chiefly negative. A human blood medium 

 was tested, resulting in a positive bacterial growth. The 

 organisms which developed as a surface growth had some 

 unusual characteristics. It was difficult to procure suffi- 

 cient quantities of human blood to make this medium on 

 a large scale, and satisfactory sterihzation of the medium 

 was extremely difficult. Special media were then devised 

 on the principle of the meat-infusion medium, in which 

 rabbit liver replaced the meat. The media were adjusted 

 to various hydrogen-ion concentrations, ranging from pH 

 6.4 to pH 8.3. When bits of liver tissue from fetal and new- 

 born rabbits were planted in these media, surface organisms 

 developed in a number of the culture tubes. In practically 

 all of the tubes that did not contain the surface organisms, 

 a pecuHar clouding developed in the culture medium about 

 the planted fiver tissue. When a part of this clouded me- 

 dium was removed from the tube, smeared on a sfide, dried, 

 fixed, stained and examined microscopically, it did not 

 contain any visible bodies that had the appearance of 

 bacteria. When wet preparations of the clouded material 

 were examined microscopically, small coccoid bodies could 

 be seen. The clouded culture media and planted tissues 

 were removed from a number of culture tubes, fixed in a 

 mitochondrial fixative, embedded in celloidin, sectioned and 

 stained. Microscopic examination of these preparations 

 revealed myriads of coccoid bodies in the clouded medium. 

 It was evident from the results of these experiments that 

 the coccoid bodies of the clouded medium were fragile, and 

 disappeared in the smear preparations from the clouded 

 medium. 



