710 REPORT 1881. 



corresponding to the work done. The results of these two experiments have been 

 found hy Professor Fick to cover each other very exactly. I have stated them in a 

 table/ in which we have the realisation as regards a single muscle of the following 

 forecast of Mayer's as regards the whole animal organism. ' Convert into heat,' 

 he said, ' by friction or otherwise, the mechanical product yielded by an animal in a 

 given time, add thereto the heat produced in the body directly during the same 

 period, and you will have the total quantity of heat which corresponds to the 

 chemical processes.' We have seen that this is realisable as regards muscle, but it is 

 not even yet within reach of experimental verification as regards the whole animal. 

 I now proceed abruptly (for the time at our disposal does not admit of our 

 spending it on transitions) to the consideration of the other great question con- 

 cerning vital motion, namely the question how the actions of the muscles of an 

 animal are so regulated and co-ordinated as to determine the combined movements, 

 whether rhythmical or voluntary, of the whole body. 



As everyone knows who has read the ' Lay Sermons,' the nature and meaning 

 of these often unintentional but always adapted motions, which constitute so large 

 a part of our bodily activity, was understood by Descartes early in the seventeenth 

 century. "Without saying anything as to his direct influence on his contemporaries 

 and successors, there can be no doubt that the appearance of Descartes was co- 

 incident with a great epoch — an epoch of great men and great achievements in 

 the acquirement of man's intellectual mastery over nature. When he interpreted 

 the unconscious closing of the eyelids on the approach of external objects, the 

 acts of coughing, sneezing, and the like, as mechanical and reflected processes, he 

 neither knew in what part of the nervous system the mechanisms concerned were 

 situated, nor how they acted. '^ It was not until a hundred years after, that Whytt 

 and Hales made the fundamental experiments on beheaded frogs, by which they 



' Relation of Product and Process in Muscle. 

 (Founded on the results of one of Fick's experiments.) 



Process. 



Sugar used 001 -4 milligrammes. 



Oxygen used 0-015 „ 



Carbonic acid gas formed .... 0'021 ,, 



Product, 



Mechanical product 6670 grammemillimeters. 



Its heat-value 1,5-6 milligrammeunits 



Heat produced .S9-0 „ 



Total product reckoned as heat . . . 54-6 „ 



* Descartes' scheme of the central nervous mechanism, comprised all the parts 

 which we now regard as essential to ' reflex action.' Sensory nerves were represented 

 by threads (iilets) which connected all parts of the body to the brain ( (Euvres, par 

 V. Cousin, vol. iv. p. 359) ; motor nerves by tubes which extended from the brain to 

 the muscles ; 'motor centres' by 'pores' which were arranged on the internal surface 

 of the ventricular cavity of the brain and guarded the entrances to the motor tubes. 

 This cavity was supposed to be kept constantly charged with ' animal spirits,' fur- 

 nished to it from the heart by arteries specially destined for the purpose. Any 

 ' incitation ' of the surface of the body by an external object which affects the organs 

 of sense does so, according to Descartes, by producing a motion at the incited part. 

 This is communicated to the pore by the thread and causes it to open, the conse- 

 • quence of which is that the 'animal spirits' contained in the ventricular cavity 

 enter the tube and are conveyed by it to the various muscles with which it is con- 

 nected, so as to produce the appropriate motions. The whole system, although it 

 was placed under the supervision of the ' dine faisonnahle ' which had its office in the 

 pineal gland, was capable of working independently. As instances of this mechanism 

 Descartes gives the withdrawal of the foot on the approach of hot objects, the 

 actions of swallowing, yawning, coughing, &c. As it is necessary that in the per- 

 formance of these complicated motions, the muscles concerned should contract in 

 succession, provision is made for this in the construction of the systems of tubes 

 which represent the motor nerves. The weakness of the scheme lies in the absence 

 of fact basis. Neither threads nor pores nor tubes have any existence. 



