20 OF THE VITAL POWERS. 



vis cellulosa. It is characterised by a simple and not 

 very sensible effort of the mucous web to contract and 

 react upon its contents, especially upon its source of 

 moisture the serous vapour, and to propel this into 

 the lymphatic system.* 



41. Irritability, we mean the irritability of Haller, is 

 peculiar to the muscles, and may be called the vis mm- 

 cularis. It is marked by an oscillatory or tremulous 

 motion, distinguished from the action of simple con- 

 tractility, by being far more permanent, and by occur- 

 ring far more easily on the application of any pretty 

 strong stimulus, f 



42. Such are the common (39) moving vital powers. 

 But some organs differ from the rest so much in their 

 structure, motions, and functions, as not to come under 

 the laws of the common orders of vital powers. We 

 must, consequently, either reform the characters of these 

 orders, institute new ones, and extend their limits, or, 

 till this be done, separate these peculiar motions from 

 the common orders, and designate them by the name of 

 vitce propri<e.$ As examples may be adduced, the 

 motions of the iris ; the erection of the nipple ; the 

 motions of the fimbriae of the Fallopian tubes ; the 

 action of the placenta and of the womb during labour ; 



* That Haller and Theoph. de Bordeu the chief writers on the mucous tola, 

 did not form a just conception of this vital power, is evident from the latter's 

 Recherchfs sur le Tissti Muqueu.r. Par.l 767. 8vo ; and from the dissertation of the 

 former on Irritability in the Dictionnaire Encyclopedique tfYverdun, T. xxv. 



t Haller, De Partibus Corp. Hum. irritabilibus in the Nov. Comm. Soc. Reg. 

 Sclent. Getting. T. iv. 



J I have spoken of these at large both in my treatise De Iridis Motu. 1784 ; 

 and my programma De Vi Vitali sa/iguini dencganda, 1795. 



