203 



calls the attention of analysts to this subject, as having frequently 

 misled them in respect to the loss obtained by subjecting minerals 

 to heat, which they have too commonly ascribed to the mere evapo- 

 ration of aqueous matter. 



Mr. Knox found bitumen in nearly all the minerals belonging to 

 Werner's Flotz Trap formation. He also found it in a few of the 

 substances appertaining to the older rocks ; but in the latter case it 

 was smaller in quantity, and less easily separable. 



In conclusion, the author recommends distillation as a process to 

 be resorted to in all analyses of stony substances, with a view of ob- 

 taining the liquid bitumen which they may have contained, and also 

 of estimating the proportion of carbon evolved in the state of gas. 

 The residuum, he observes, should be carefully examined for the re- 

 maining carbon. 



On certain Changes which appear to have taken place in the Positions 

 of some of the principal fixed Stars. By John Pond, Astronomer 

 Royal, F.R.S. Read June 19, 1823. [Phil. Trans. 1823, p. 529.] 



The Croonian Lecture. On the Internal Structure of the Human Brain, 

 when examined in the Microscope, as compared with that of Fishes, 

 Insects and Worms. By Sir Everard Home, Bart. V.P.R.S. 

 Read November 20, 1823. [Phil. Trans. 1824,^. 1.] 



In this lecture the author pursues his researches respecting the 

 anatomy of the human brain, and compares it with that of fishes, 

 insects, and worms, in the hope of developing the connexion between 

 the action of the nerves and the motion of the muscles. To obviate 

 the sources of error attendant upon the usual methods of dissecting 

 and examining the brain, a portion of it in a very recent state was 

 submitted to the microscope, after having been immersed in distilled 

 water. Rows of globules were thus detected passing in straight lines 

 from the circumference of the cortical substance into the medullary 

 portion, the appearance of which is shown by Mr. Bauer in an an- 

 nexed drawing. From a representation, also by Mr. Bauer, of the 

 tench, it appears that its relative proportion to the size of the 

 animal is smaller than in the bird, that it has a central cavity and 

 a nodulated basis. In insects the brain contains, and its principal 

 portion is connected by, nervous chords, with what is usually called 

 a ganglion, but which, when examined accurately, is found to re- 

 semble the brain in texture, and which, from the office of the nerves 

 it sends off, the author considers, as Medulla oblongata. Below this is 

 a regular line of ganglions united by a double nerve, the details of 

 these structures being illustrated by annexed drawings. 



Among insects the bee has the largest proportion of brain relative 

 to the size of its body. In the moth and caterpillar it is smaller, but 

 similar in structure, as also in the lobster. In the garden snail the 

 brain is relatively larger than in the bee, but there are no ganglions, 

 although the structure of the Medulla spinal is is the same. 



