THE 
VETERINARIAN. 
VOL. X, No. 112.] APRIL 1837. [New Series, No. 52. 
ANIMAL PATHOLOGY. 
By Mr, Youatt. 
LECTURE X ( concluded ), 
The Pulmonary Plexus- 
WE now arrive at those organs by which the most important 
function of life is performed, or rather where that is accom- 
plished which is absolutely necessary to the development and to 
the continuance of life. It matters not that nutritive substances 
are received into the stomach, and separated from the ingredients 
which are excrementitious and useless, and carried on to one 
common receptacle, and the heart is ready to convey them to 
every part of the frame; a preliminary process must be effected 
ere one act of nutrition or secretion, or one manifestation of 
muscular power or nervous energy, can take place ; and that is, 
the exposure of these fluids to the influence of the atmospheric 
air, or, in other words, the arterialization or vivification of the 
blood, accomplished by means of the seemingly complicated 
yet simple and admirable structure of the lungs. We have just 
considered the power exerted by the laryngeal branches of the 
spinal organic nerve over the dilatation and expansion of the tube 
by means of which the air is conveyed from the nasal passages 
and the posterior part of the mouth to the entrance into the 
lungs. The superior laryngeal nerves contract, the inferior 
dilate the tube, and particularly the entrance into it, and regu- 
late the calibre of the tube and the supply of air according to 
the state of the constitution or the muscular exertion which at 
the time is required ; the transversalis muscle, so evident in the 
horse, securing the windpipe from laceration when, in the some- 
times cruel exertion of speed, the air rushes furiously along, or 
when violent pressure is made upon it from without. In certain 
states of disease of the respiratory organs, much advantage will 
be derived from this power of regulating the calibre of the air- 
vol. x. a a 
