OLD AGE. 543 



old ngL\ by the work of the giant cells designated under the name of 

 osteoclasts. 



Since the mechanism of senile atrophy is entirely similar to that of 

 atrophies of microbic or toxic origin, it may be asked whether in old 

 age there may not be some intervention of microbes or their poisons. 

 Ma}^ not this abnormal excitation of the macrophages that leads 

 them to destroy all sorts of noble cells of the organism and to even 

 attack the pigment of the hair and the osseous substance be also due 

 to the action of certain poisons elaborated within the body? The 

 principal source of these poisons is clearly indicated: our digestive 

 tube contains an enormous (pumtity of microbes, and numy of them 

 are capable of secreting substances that are more or less toxic. Our 

 intestinal flora resembles the flora or forests in which there are 

 found by the side of boleti and other edible nnishrooms a great num- 

 ber of poisonous ones. It is true that our intestine is, up to a certain 

 point, protected against the invasion of the microbes contained in it 

 and CA'en against their poisonous products. We may with impunity 

 feed animals that are quite easily affected by certain infectious mala- 

 dies upon the microbes that produce those maladies. Thus guinea 

 pigs may swallow without harm great quantities of the l)acilli that 

 produce anthrax, but if there is the least lesion in the intestinal wall 

 the mortal malady wall declare itself. The presence of inf(M-tious 

 microbes in the digestive tul)e may therefore have sad results. 



The intestine is likewise protected against the absorption of certain 

 poisons. We may, for example, cause guinea pigs to swallow, with- 

 out effect, many cul>ic centimeters of tetanic poison, a hundredth part 

 of a drop of which injected under the skin will inevital)ly bring on a 

 uiortal tetanus. The intestinal wall does not, therefore, absorb the 

 tetanic poison. There are, however, other poisons that do not follow 

 this rule and which are easily absorbed in the intestine. Cases of 

 poisoning by })oisonous mushroooms taken for edible ones are quite 

 frefpient. Neither is there any lack of microbic poisons that traverse 

 the intestinal wall. We see arise from time to time veritable ei)i- 

 demics that are serious and even fatal as a consequence of the con- 

 sumption of fish, meat, or conserves spoiled by microbes. In these 

 cases there is usually an entrance into the intestines of the botulynic 

 bacillus, which secretes a very violent poison readily absorbed by the 

 organism in the same way as is the poison from noxious nnishrooms. 

 The symptoms of Asiatic cholera are also produced by a toxine elab- 

 orated in the digestive tube and absorbed by the intestinal wall. 



But in the cases which we have just cited there occurs an acute 

 poisoning, occasioned by the toxic products of microbes and of mush- 

 rooms introduced into the intestines. Now, there is no doubt but 

 that there occur besides these examples others in which the poisoning 

 is less violent and less rapid and in which the microbes of the intes- 



