declination. The results which he has obtained are utterly irrecon- 

 cilable with the theory of Bernoulli, and therefore the tables com- 

 puted upon that theory must be rejected as inaccurate. 



A paper was also read, entitled, " On the Nature of Sleep." By 

 A. P. W. Philip, M.D. F.R.S.L.&E. 



The author intends the present paper as a continuation of his in- 

 quiries into the relations subsisting between the nervous and muscu- 

 lar systems, which form the subject of his former papers, but which 

 would be incomplete without the consideration of their condition 

 during sleep. With this view he proposes to determine the particular 

 organs, on the condition of which this peculiar state of the system 

 depends ; the laws by which it is governed ; and the influence it has 

 upon other parts of the system. The necessity of intervals of repose 

 applies only to those functions which are the medium of intercourse 

 with the external world, and which are not directly concerned in the 

 maintenance of life. The organs subservient to these two classes of 

 functions may be viewed as in a great degree distinct from one an- 

 other. The brain and spinal marrow constitute alone the active por- 

 tions of the nervous system. The law of excitement, which regulates 

 the parts connected with the sensorial functions, including sensation, 

 volition, and other intellectual operations, and the actions of the vo- 

 luntary muscles, is uniform excitement, followed by a proportional 

 exhaustion j which, when occurring in such a degree as to suspend 

 their usual functions, constitutes sleep ; all degrees of exhaustion 

 which do not extend beyond the parts connected with the sensorial 

 functions being consistent with health. On the other hand, the law 

 of excitement of those parts of the brain and spinal marrow which are 

 associated with the vital nerves, and are subservient to the vital func- 

 tions, is also uniform excitement ; but it is only when this excitement 

 is excessive that it is followed by any exhaustion ; and no degree of 

 this exhaustion is consistent with health. The law of excitement of 

 the muscular fibre, with which both the vital and sensitive parts of the 

 brain and spinal marrow are associated, namely, the muscles of respi- 

 ration, is interrupted excitement, which, like the excitement of the 

 vital parts of these organs, is, only when excessive, followed by any 

 degree of exhaustion. The author conceives that the nature of the 

 muscular fibre is everywhere the same ; the apparent differences in 

 the nature of the muscles of voluntary and involuntary motion de- 

 pending on the differences of their functions, and on the circumstances 

 in which they are placed : and he concludes, that, during sleep, the 

 vital, partaking in no degree of the exhaustion of the sensitive system, 

 appears to do so simply in consequence of the influence of the latter 

 on the function of respiration, the only vital function in which these 

 systems co-operate. 



The author proceeds to make some observations on the cause of 

 dreaming, the phenomena of which he conceives to be a natural con- 

 sequence of the preceding proposition. In ordinary sleep, the sen- 

 sitive parts of the brain, with which the powers of the mind are asso- 

 ciated, are not in a state of such complete exhaustion as to preclude 

 their being excited by slight causes of irritation, such as those which 



