Mr. W. Huggins on the Spectrum of Comet II., 1868. 393 



ence in the functional activity of the brain and cord, the need for 

 sleep by the brain, not experienced, at any rate in the same degree, 

 by the cord, point to a difference of tension, and therefore of relation 

 to the substances which act as poisons. This consideration will 

 apply where the differences of susceptibility and of tension are not 

 so marked. 



But this is only part of a still wider question — the different action 

 of poisons on different classes of animals. The explanation is still 

 the same. Difference in the functional energy or activity of corre- 

 sponding nerve-centres implies difference of tension. 



The following facts bear strikingly on this point : — 



1 . Anaesthetics affect all classes of animals alike, i. e. when the 

 effect is a general arrest of oxidation. 



2. Strychnia, which acts on the cord, affects all animals alike. 

 The spinal system is the centre which is most similar in its endow- 

 ments in all classes of vertebrates. 



3. The poisons which have the most diverse action on different 

 animals are such as in man act on the cerebral ganglia. 



" On the Spectrum of Comet II., 1868." By William Huggins, 

 F.R.S. 



The author describes the appearance of the comet in the tele- 

 scope on June 22 to consist of a nearly circular coma, which became 

 rather suddenly brighter towards the centre, where there was a nearly 

 round spot of light. A tail was traced for nearly a degree. 



He found the light of the comet, when examined with a spectro- 

 scope furnished with two prisms of 60°, to be resolved into three 

 broad bright bands. 



The brightest band commences at about b, and extends nearly 

 to F. Another band begins at a distance beyond F rather greater 

 than half the interval between b and F. The third band occurs 

 about midway between D and E. In the two more refrangible of these 

 bands the light was brightest at the less refrangible end, and gradually 

 diminished towards the other limit of the bands. The least refran- 

 gible of the three bands did not exhibit a similar gradation of bright- 

 ness. 



These bands could not be resolved into lines, nor was any light 

 seen beyond the bands towards the violet and the red. 



The measures of these bands are given, and a diagram of their 

 appearance. 



The author found this cometic spectrum to agree exactly with a 

 form of the spectrum of carbon which he had observed and measured 

 in 1864. When an induction spark, with Leyden jars intercalated, 

 is taken in a current of olefiant gas, the highly heated vapour of car- 

 bon exhibits a spectrum which is somewhat modified from that which 

 may be regarded as typical of carbon. The light is of the same 

 refrangibilities, but the separate strong lines are not to be distin- 

 guished. The shading (composed of numerous fine lines) which 

 accompanies the lines appears as an unresolved nebulous light. 



On June 23 the spectrum of the comet was compared directly 



