702 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



artificial Tetanus induced by Strychnine; in which the slightest external 

 stimulus is sufficient to induce reflex actions in their most terrific forms. It is 

 interesting to remark that, in this formidable disease, the functions of the 

 muscles controlling the various orifices are those most affected ; and it is by the 

 spasms affecting the organs of respiration or deglutition, that life is commonly 

 terminated. In some forms of Hysteria, also, there is a morbid excitability of 

 the same kind, so that various kinds of convulsions are brought on by very 

 slight stimuli ; and Infantile convulsions are generally attributable to the same 

 kind of disorder of the nervous centres, which is frequently induced by bad air, 

 unwholesome food, or some other cause that affects the purity of the blood 

 ( 583). Not only is the general muscular system of Animal life involved in 

 these abnormal actions, but various parts of the apparatus of Organic life have 

 their normal functions seriously perverted by the same condition of the Spinal 

 Cord ; being connected with it through the medium of the Sympathetic system 

 of nerves, whose motor powers are chiefly, if not entirely, derived from that 

 source (Sect. 6). Various remedial agents will probably be found to operate, 

 by occasioning increased excitability in some particular segments of the Cord ; 

 so that the usual stimuli applied to the parts connected with these will occasion 

 increased muscular tension. This seems to be the case, for example, in regard 

 to the influence of aloes on the rectum and uterus, cantharides on the neck of 

 the bladder and adjoining parts, and secale cornutum on the uterus. The mode 

 of influence of cantharides is illustrated by a curious case, related by Dr. M. 

 Hall, of a young lady who lost the power of retention of urine, in consequence of 

 a fatty tumor in the spinal canal, which gradually severed the Spinal Cord, and 

 induced paraplegia. The power of retaining the urine was always restored far 

 a time by a dose of tincture of cantharides, which seems to have acted by 

 augmenting the excitability of that segment of the Cord with which the sphinc- 

 ter vesicse is connected. 



3. Of the Sensory Ganglia and their Functions. Consensual Movements. 



729. At the base of the Brain in Man, concealed by the Cerebral Hemi- 

 spheres, but still readily distinguishable from them, we find a series of ganglionic 

 masses; which are in direct connection with the nerves of Sensation; and which 

 appear to have functions quite independent of those of the other components of 

 the Encephalon. Thus anteriorly we have the Olf active ganglia, in what are 

 commonly termed the bulbous expansions of the Olfactive nerve. That these 

 are real ganglia is proved by their containing gray or vesicular substance; and 

 their separation from the general mass of the Encephalon, by the peduncles or 

 footstalks commonly termed the trunks of the Olfactory nerves, finds its analogy 

 in many species of Fish. The ganglionic nature of these masses is more evident 

 in many of the lower Mammalia, in which the organ of Smell is highly developed, 

 than it is in Man, whose olfactive powers are comparatively moderate. At some 

 distance behind these, we have the representatives of the Optic ganglia, in the 

 Tubercula Quadrigemina, to which the principal part of the roots of the Optic 

 nerve may be traced. Although these bodies are so small in Man, in compari- 

 son with the whole Encephalic mass, as to be apparently insignificant, yet they 

 are much larger, and form a more evidently important part of it in many of the 

 lower Mammalia; though still presenting the same general aspect. The Audi- 

 tory ganglia do not form distinct lobes or projections ; but are lodged in the 

 substance of the Medulla Oblongata. Their real character is most evident in 

 certain Fishes, as the Carp ; in which we trace the Auditory nerve into a gan- 

 glionic centre as distinct as the Optic ganglion. In higher animals, however, 

 and in Man, we are able to trace the Auditory nerve into a small mass of vesi- 

 cular matter, which lies on each side of the Fourth Ventricle; and although this 



