NERVES OF SPECIAL SENSE. 651 



pulses in respondence to sensations excited through the former. They are 

 also intimately connected with other ganglionic masses in their neighborhood, 

 such as the " locus niger," and the vesicular matter of the " tuber annulare ;" 

 which, atraiu, are in close relation with the vesicular matter of the Medulla 

 Oblongata. 



514. It has been commonly supposed that the fibres of the Crura Cerebri, 

 after entering the Corpora Striata and Thalami Optici, pass continuously 

 through these bodies, receiving " reinforcements " of additional fibres from 

 their gangliouic matter; and that they then radiate to the internal surface 

 of the gray matter of the Cerebral Hemispheres. Such would certainly be 

 the conclusion to which a superficial examination of their course would lead. 

 But very strong reasons have recently been advanced for the belief, that the 

 fibres of the Crura Cerebri for the most part, if not entirely, terminate in the 

 vesicular substance of the Corpora Striata and Thalami Optici ; and that the 

 radiating fibres of the Hemispheres take a fresh departure from these ganglia, 

 serving, in fact, the part of commissures to connect their vesicular substance 

 with that of the Cerebral ganglia. 1 And this view, as we shall hereafter see, 

 is in complete accordance with the existence of a very decided physiological 

 separation between these two sets of organs. Altogether it is very evident, 

 that a series of true ganglionic centres exists at the base of the Eucephalon, 

 which are really as distinct from either the Cerebrum or Cerebellum as 

 the latter are from each other ; and as these centres are in immediate con- 

 nection with the nerves both of special and of general Sense, they may be 

 appropriately designated the Sensory Ganglia. An inqury into the distribu- 

 tion and endowments of their nerves will assist us in the determination of the 

 functions of the central organs in which they terminate. 



515. Nerves of Special Sense. Through the First pair, or Olfactory nerve, 

 are transmitted the impressions made by odorous emanations upon the sur- 

 face it supplies ; and it is not susceptible to impressions of any other kind. 

 Anatomical examination of the distribution of this nerve proves that it is 

 not one which directly conveys motor influence to any muscles, since all its 

 branches are distributed to the membrane lining the nasal cavity; and ex- 

 perimental inquiry leads to the same result, for no irritation of the peduncles 

 or branches excites any muscular movement. Further, no irritation of any 

 part of this nerve excites reflex actions through other nerves. Again, it is 

 not a nerve of "common" sensation ; for animals exhibit no signs of pain 

 when it is subjected to any kind of irritation. Neither the division of the 

 nerve, nor the destruction of the olfactive ganglia, seems to inconvenience 

 them materially. They take their food, move with their accustomed agility, 

 and exhibit the usual appetites of their kind. The " common " sensibility of 

 the parts contained in the olfactive organ is in no degree impaired, as is shown 

 by the effects of irritating vapors; but the animals are destitute of the sense 

 of smell, as is shown by the way in which these vapors affect them ; for at first 

 they appear indifferent to their presence, and then suddenly and vehemently 

 avoid them as soon as the Schueideriau membrane becomes irritated. More- 

 over, if two dogs, with the eyes bandaged, one having the olfactory nerves 

 and ganglia sound, and the other having had them destroyed, are brought 

 into the neighborhood of the dead body of an animal, the former will ex- 

 amine it by its smell ; whilst the latter, even if he touches it pays no atten- 

 tion to it. This experiment Valentin 2 states that he has repeated several 

 times, and always with the same results. Further, common observation 



1 See especially Messrs. Todd and Bowman's Physiological Anatomy, vol. i, p. 277; 

 and Prof. KSlliUer's Mikroskopische Anatomie, Bd. ii, \ 118. 



2 De Functionibus IServoruui Cerebraliurn, etc., Berna?, 1839. 



