160 Dr Craigie's Observations on the 



erroneous physiology of the times, and ignorance of the separate 

 uses of the arteries and veins, exhibits, nevertheless, some accu- 

 rate facts which shew the diligence of the author in dissection. 

 Though, in opposition to the opinions of Praxagoras and Era- 

 sistratus, he proved that the arteries in the living animal con- 

 tain not air, but blood, it does not appear to have occurred to 

 him to determine in what direction the blood flows, or whether 

 , it was movable or stationary *, Representing the left ventricle 

 of the heart as the common origin of all the arteries, though he 

 is misled by the pulmonary artery, he nevertheless traces the 

 distribution of the branches of the aorta with some accuracy. 

 The X)€na azygos, also, and the jugular veins, have contributed 

 to add to the confusion of his description, and to render his an- 

 giology the most imperfect of his works. 



In neurology, we find him to be the author of the dogma, 

 that the brain is the origin of the nerves of sensation, and the 

 spinal chord of those of motion ; and he distinguishes the for- 

 mer from the latter by their greater softness or less consistence. 

 Though he admits only seven cerebral pairs, he has the merit 

 of distinguishing and tracing the distribution of the greater part 

 of both classes of nerves with great accuracy. 



His description of the brain, though derived from dissection 

 of the lower animals, is accurate ; and his distinctions of the 

 several parts of the organ have been retained by modern ana- 

 tomists. His mode of demonstrating this organ, which indeed 

 is clearly described, consists of five different steps. In the 

 first, the bisecting membrane, i. e. the falx (^myl ^ixorof^ovc-xy^ 

 and the connecting bloodvessels are removed ; and the dis- 

 sector, commencing at the anterior extremity of the great fis- 

 sure, separates the hemispheres gently as far as the torcular, 

 and exposes a smooth surface (-my x'^^'^^ TvX6>h Trag cva-ctv)^ the 

 mesolobe of the moderns, or the middle band. In the second, 

 he exposes, by successive sections, the ventricles, the choroid 

 plexus, and the middle partition. The third exhibits the 

 conoid body {(rafAo, Kmouhg) or conarium, or pineal gland of the 

 modern anatomists, concealed by a membrane with numerous 

 veins, meaning that part of the plexus which is now known by 

 the name of velum interpositum, and a complete view of the 



• Tlt^t AvKTOfAiKuv "Ey^ii^yiiriuv, lib. vii. 



