LIFE AND WRITINGS OF EGBERT WHYTT, M.D. 115 



readily have been made by Whytt. The next quotation shows an advance upon 

 Whytt's ideas. 



" It certainly does not appear that the whole of the cerebrum and cerebellum 

 enters into the constitution of the sensorium commune, for the former portions 

 of the nervous system seem rather to be the instruments that the soul directly 

 uses for performing its own actions, termed animal ; but the sensorium commune, 

 properly so called, seems not improbably to extend through the medulla oblon- 

 gata, the crura of the cerebrum and cerebellum, also part of the thalami optici, 

 and the whole of the medulla spinalis ; in a word, it is co-extensive with the 

 origin of the nerves. * * * Xhe reflexion of sensorial into motor impres- 

 sions, which takes place in the sensorium commune, is not performed according 

 to mere physical laws, where the angle of reflexion is equal to the angle of inci- 

 dence, and where the reaction is equal to the action ; but that reflexion follows 

 according to certain laws, writ, as it were by nature, on the medullary pulp of 

 the sensorium, which laws we are able to know from their effects only, and 

 nowise to find out by our reason. * * * Since the principal function of the 

 sensorium thus consists in the reflexion of sensorial impressions into motor, it is 

 to be noted that this reflexion may take place either with consciousness or without 

 consciousness." 



Thus reflex action in the hands of Prochaska amounts to this, that it has its 

 seat in the commune sensorium, or that part of the nervous centre which, exclud- 

 ing the cerebrum and cerebellum, is sometimes named the cranio-spinal axis. 

 He differs from Whytt, therefore, in excluding the cerebrum and cerebellum 

 from any share in the function ; and while his language is not the same as 

 Whytt's, because he adopts the term law to express its character, which Whytt 

 had refused to use, he is essentially of the same way of thinking with Whytt, 

 inasmuch as he says the law is written on the medullary pulp of the sensorium, 

 which is merely another mode of stating that there is something behind that 

 pulp whereby the effect is produced. 



Before leaving Prochaska, however, reference must be made again to the 

 share Whytt had in fostering and insisting on the assumption of the complete 

 isolation of the minute fibrils composing the nerves. Prochaska, who was well 

 versed in the literature of the nervous system, refers to the isolation of the fibrils 

 of the nerves as a conjecture of Whytt's, while he rejects it as an improbability. 

 Nevertheless Unzer distinctly says, that no confusion of impressions brought by 

 separate channels to the brain occurs, because the nerve-fibrils are isolated. 

 Here he seems manifestly to contradict himself in a passage before referred to, 

 in which he says, that " the impression is transmitted along the nerve upwards 

 towards the brain ; but ere it reaches there, it is turned from its course, and so 

 reflected downwards, that it excites (like an internal impression) the nerve of the 

 other remote parts or the nerve twigs, or efferent nerve-fibrils of the part receiv- 

 VOL. xxni. part I. 2 I 



