TRANSMISSION OF MICRO-ORGANISMS. 327 



the lower animals, and the evidence that bacteria may in 

 this manner gain access to the organism is incontestable. 



In inherited specific diseases it is possible to distinguish 

 two forms of infection : first, by a direct bacterial invasion of 

 the essential reproductive cells ; secondly, the egg-cell or 

 the embryo may receive micro-organisms from the female, 

 in which case the blood stream is the channel for conveyance, 

 and the whole phenomenon is then one of metastasis com- 

 parable in every respect to what obtains when bacteria 

 multiply at a definite area of the body, and thence become 

 distributed by the blood and lymph in distant parts of the 

 organism. Bacterial infection may therefore be either 

 germinative or placental, and in mammals the latter 

 form of transmission is not infrequently observed. The 

 specific bacteria of anthrax, typhoid fever (6), pneumonia 

 and tuberculosis (7) have been isolated from the human foetus, 

 cultivated, and successfully inoculated upon animals, so 

 that the chain of evidence is complete. The pyogenic 

 cocci such as streptococcus pyogenes (24) and staphylococcus 

 pyogenes aureus have also been demonstrated in foetal 

 tissues by Fraenkel and Kiderlen, and Auche has shown 

 that in small-pox the placenta may be penetrated by these 

 micro-organisms. In the lower animals not only may the 

 bacteria already mentioned be transmitted, but also those of 

 cholera, glanders and chicken cholera. 



In many animals the egg-cell is the largest unit of the 

 organism, and would be capable of containing numberless 

 bacteria ; that such an infection does occur was first estab- 

 lished by the classical observations of Pasteur (4), which 

 have been confirmed by all subsequent investigators. In 

 pebrine, a disease of silk-worms, definite sporocyst forms 

 (microsporidia or Cornalia's corpuscles) are transmitted from 

 the imago in the egg-cell, and the larva is directly infected 

 in this manner. Blochmann (5) has also described a similar 

 mode of conveyance of bacteria in the ova of Blatta 

 orientalis. In a single instance a tubercle bacillus has 

 been seen in the mammalian ovum. The sperm-mother- 

 cells may also be invaded by micro-organisms, but this is 

 rare, and no example of an infected male reproductive cell 



