540 OLD AGE. 



more slowly than elseAvhere. On the other hand, in boys from 11 to 

 1 5 years old, studied by this observer, the rapidit}^ of development of 

 the hair Avas always shown to be less than 15 mm. It was often even 

 below the 11 mm. found in the man 61 years old. 



In spite of the abundant growth of the hair in old age, these parts 

 undergo a senile degeneration; that is to say, the loss of pigment. 

 This blanching is doubtless an atrophic phenomenon which is not duo 

 to an arrest of cellular multiplication, but to the disappearance of 

 colored granulations. 



Let us now cast a glance at some other manifestations of old age. 

 The debility of muscular movements is connected with modifications 

 in the structure of the muscular fibers which also do not indicate an 

 absence of reproductive power. The fascicles Avhich form the mus- 

 cles undergo a veritable atrophy, for they become much thinner than 

 in their normal state. Besides there is deposited in their interior a 

 quantity of fatty granulations, and, Avhat specially merits attention, 

 the nuclei of the muscular fibers show a very abundant multiplica- 

 tion, forming masses arranged in long series. Douaud, who has 

 published a thesis ujDon the modifications of muscles in old age, 

 remarks in this connection that the endogenous multiplication of 

 muscular nuclei in old age is very active and that it takes place in 

 exactly the same way as in the embryo. In this example of senile 

 atrophy we are far then from finding a cessation of reproductive 

 power in the cells. 



As regards the brittleness of the bones in old people, this is also 

 caused by cellular multiplication which i:)roduces large cells capable 

 of destroying the osseous substance and making the bones spong^^ 



Detailed microscopic observation of senile organs has shown in a 

 direct manner the existence of cellular multiplication. Thus Sacka- 

 roff observed it in the lymphatic ganglia of old persons, and among 

 others in a man 102 years old. The few data just cited suffice to 

 enable us to reject the theory that old age is caused by the exhaustion 

 of the reproductive faculty of the cells. We must seek for another 

 more comformable with the well-established facts of senile degeneres- 

 ence. Without entering upon new details, let us try to comprehen- 

 sively survey those we have already given. A\^iat common features 

 connect the blanching of the hair with the atrophy of muscular 

 fibers and the brittleness of the bones of the aged ? 



The loss of colored granulations in the hair is due to the setting free 

 of a quantity of Avandering cells which seize the pigment and trans- 

 port it elsewhere, leaving the hair decolorized. In the atrophy of 

 the muscles there is a nniltiplication of the nuclei and of the substance 

 that surrounds them. xVs in the hair there are cells which dcxoiir 

 the pigment, so in the muscles there are the multiplied elements we 

 have just cited which devour the contractile substance. In senile 



