OLD AGE. 545 



which I observed vei'v dosely for several years, iiuinifesled no si<riis 

 whatever of ohl a<;:e. It was very lively and curious, interest in<; 

 itself in all sorts of things about it, and its plumage was brilliant and 

 richly coloi-ed. We ha\e j)ossessed for some years j)ast a parrcxjuet 

 that, according to reliable information, must be from 70 to 75 years 

 old. It is impossible to recognize its advanced age, so normal is its 

 ap})earance and so easy are its movements. 



The few examples just cited confirm the general rule that i)irds 

 iiave a nuich geater longevity than the large majority of nuimmals. 

 Now. birds are distinguished l)v having an intestinal flora very much 

 ])0()rer in microbes than that of mannnals. Possessing no large intes- 

 tiiie, birds lack that great reservoir for alimentary refuse which, in 

 mannnals. breeds an enormous (luantity of all sorts of microbes. A 

 very simple method of assuring ourselves of this consists in a micro- 

 scopic examination directed toward ascertaining the comparative 

 ([uantity of microbes contained in different parts of the digestive tube 

 of a small nutmmal, a white mouse for example. We find quite a 

 large number in the stomach; very few in the upper portions of the 

 small intestine. The lower part of the small intestine contains many 

 microbes, but it is in the caecum and the large intestine that are found 

 ([uantities truly enormous. The examination of the digestive organs 

 of a small bird, a canary for example, having the same weight as the 

 mouse above mentioned, gives quite a difi'erent result. In canaries 

 microbes are found, but in very small numbers. The stomach and the 

 small intestine contain throughout their course only a few isolated 

 specimens. The inferior portion of the intestinal tract contains a few 

 more microbes, but their number is very far from being equal to that 

 found in the mouse. The caecum, that large reservoir for intestinal 

 microbes in the mouse, is represented in the canary merely by two 

 rudimentary culs de sac destitute of microbes. It is not astonishing 

 that, under these conditions, the toxic effects derived from intestinal 

 sources slioidd be much less in the canary (and in birds in general) 

 than in the mouse and most other animals. So we see that while the 

 mouse is already old after a few years, and lives hardly five years at 

 most, the canary is vigorous foi- a nuich longer period and may attain 

 the age of 15 or even 20 years. 



When Ave see that cold-blooded vertebrates, such as turtles and 

 crocodiles, attain a very advanced age without showing any extensive 

 signs of senility, we are tempted to ascribe this fact to the rather 

 inactive life of those animals. As they do not need to maintain a 

 high bodily temperature, they take but little food and are not forced 

 to expend much energy in procuring it. Birds have none of these 

 advantages. They lead a very active and agitated life; in order to 

 preserve their normal condition they must maintain a higher bodily 

 SM 1904 35 



