OLD AGE. 543 



old iiii't', l)y tlio woi-lv of tho i2:ianl colls (losif;nato(l undor (he iiiiinc of 

 osteoclasis. 



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

 atrojohies of niicrobic or toxic origin, it may be asked whether in old 

 a<>e there may not be some intervention of microbes or their poisons. 

 May 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 Avithin the body? The 

 principal source of these poisons is clearly indicated: our digestive 

 tube contains an enormous quantity of microbes, and many 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 mushrooms a great num- 

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

 [)oint. protected against the invasion of the microbes contained in it 

 and cAcn 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 bacilli that 

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

 the mortal malady will declare itself. The presence of infectious 

 udcrobes in the digestive tube 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 cubic centimeters of tetanic poison, a hundredth part 

 of a drop of which injected under the skin will inevitabh' bring on a 

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

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

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

 l>oisoning by poisonous mushroooms taken for edible ones are quite 

 frequent. Neither is there an}' lack of niicrobic poisons that traverse 

 the intestinal wall. We see arise from time to time veritable e]M- 

 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 b}^ the 

 I organism in the same way as is the poison from noxious mushrooms. 

 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 w'e 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- 



