390 INNERVATION. [CHAP. XII. 



The consentaneous action of symmetrical parts is no doubt due to 

 a similar cause to that by which most of the sympathetic actions are 

 excited, and more especially in those parts where symmetry of 

 action is constant, although liable to be interrupted by the influence 

 of the will. 



A distinct class of sympathetic actions consists of those in which 

 certain parts enlarge or become developed simultaneously with, and 

 to a certain extent as an effect of, the increase of others. The penis, 

 the beard, the vocal organs, experience a marked increase of de- 

 velopment at the adult period of life simultaneously with the 

 enlargment of the testes ; and it may be added, in effect of their in- 

 crease, because the early removal of these organs prevents the growtl 

 of the others. And so likewise as the ovaria are developed, the uterus 

 the vulva, the mammae, increase in size ; the ovarian and uterim 

 irritation which accompanies the menstrual flux causes enlargement 

 of the breasts, which subsides as soon as that period has gone by. 



The various examples enumerated in the preceding paragrapl 

 may be classed under three heads : first, sympathies between dif- 

 ferent individuals; secondly, those which affect the mind, an< 

 through it, the body ; and, thirdly, those which are strictly organic 

 and therefore physical. 



Of the first class of sympathies we can offer no physical explanj 

 tion. Whether the nervous system of one individual can directly 

 affect that of another, or whether the effect is produced on the iim 

 gination, and afterwards on the nervous system, are questions stil 

 sub judice. The serpent fascinates his prey, apparently by th< 

 power of his eyes, and it is well known that one man can exert 

 marked control over another by a mere look ; and in the same w 

 men can control other animals, even the fiercest carnivora, by a firm 

 and decided glance of the eyes. It is no explanation of sympathetic 

 phenomena of this kind to ascribe them to the effect of a tendency 

 to imitation. Imitation is voluntary ; these actions are involuntary, 

 or take place even in despite of the will.* 



In the second class of sympathetic phenomena, an affection of th< 

 mind is a necessary link. But why that affection of the mind shoulc 

 produce its peculiar effect is a question of difficult solution. 

 should the perception of certain odours produce in one case increased 

 action of the salivary glands, and in the other case cause syncope? 

 The only reply which can be made to this question is, that in these 

 instances the impression on the sensorium causes a change there 

 analogous to that which an original affection of the mind of similar 

 * Bostock's Physiology, vol. iii. p. 227. 



