108 ANIMAL-SENTIENT FORCES. [i. 



takes place into the cavities. This action is the greater in pro- 

 portion as the sensation is more vivid. Hence contra-natural 

 inflammations and swellings in the muscles and other me- 

 chanical machines arise from painful external sensations. From 

 pleasant sensations, as warmth, friction, itching, titillation, arise 

 a gentle glow and excitement ; and in cavities, such as the nares, 

 or intestines, in which the capillaries can pour out their con- 

 tents, an accumulation of fluid, as, for example, a discharge from 

 tickling of the nose (199), a purging from colicky pain, purgatives, 

 poison, &c. (198.) This afflux of fluids to the mouths of these 

 capillary vessels, when an external sensation stimulates their 

 own nerves, or by sympathy, those adjoining (165), constitutes 

 the basis of many important phenomena in the animal economy, 

 and has the most important bearing on the instincts, emotions, 

 and diseases of animal organisms, (Haller's ' Physiol.,' § 561.) 

 The greater number of mechanical machines of the body are 

 as thoroughly interpenetrated by capillary vessels as by nerves ; 

 it follows, therefore, that this particular action of external sen- 

 sations is observed to be almost always coincident with all 

 external impressions which are felt ; and thus it is a general 

 physiological law, that concurrently with each external sensation 

 there is an afflux of fluid to the point where the external im- 

 pression is made. This is not, however, the sole law, nor is it 

 quite general, since this afflux cannot take place as a consequence 

 of external sensation ia those parts not supplied with capillaries 

 and tubuli ; nor does it even take place in other parts, if the 

 external sensation be not of a certain degree of intensity or 

 strength. 



208. External sensations excite direct sentient actions in the 

 flat muscles, particularly the diaphragm (171), which consist of 

 such contractions, or other movements, as they are capable of, 

 in virtue of their structure (193). Thus a painful sensation 

 from inflammation of the diaphragm, causes unnatural respira- 

 tion, in consequence of the convulsive movement excited in it. 

 Those membranes of the organism, which do not consist of a 

 true muscular tissue, but rather of minute glands, papillae, cel- 

 lular tissue, and capillaries and tubuli, must be considered quite 

 difi'erently with reference to their sensibility, and the sentient 

 actions resulting therefrom. Some of these membranes have 

 numerous nerves, and are very sensitive, as the skin, and the 



