THE NERVOUS SYSTEM. 99 



rence, is called delirium tremens. It arises from the continued 

 abuse of ardent spirits. There are three organs especially affected 

 by this baneful habit the brain, the liver, and the kidneys. The 

 two latter slowly, but surely, become diseased, and their diseases 

 generally prove fatal. Delirium tremens, however, though a dan- 

 gerous, is not usually a fatal disease. The person affected is in a 

 high state of excitement, thinks he is surrounded by evil spirits, 

 imagines all his friends are plotting against him, and a thousand 

 other fancies. The mind, in certain other states and diseases, is 

 also very singularly affected, which it would be curious to refer to, 

 did our space permit. Dr. Abercrombie's work on the intellectual 

 powers, the works of phrenologists, those on somnabulisnr and 

 animal magnetism, &c., contain some very interesting facts on this 

 subject. 



[To illustrate this section, the brain of a sheep may be exhibited, which can easily 

 be done by sawing through the skull from behind the eyes down to the opening for the 

 spinal marrow (taking care not to saw too deep), and then wrenching it off with a 

 screw-driver or other strong lever. The membranes covering the brain will be observed. 

 These should be slit open, and the brain lifted up anteriorly, when the different nerves, 

 commencing with the olfactory, will come into view, and must be cut through, and the 

 brain taken out and placed in spirits for a few hours to harden it. The nerves, as seen 

 in Fig. 33, the ventricles in the interior of the brain, and the other parts described 

 here, and in anatomical works, may then easily be seen. A cod's or haddock's brain 

 and spinal marrow may easily be shown, by cutting with a strong pair of scissors the 

 spinal rings and the skull. 



Besides these, if wished, the progressive development of the brain in different species 

 may, with a little care and patience, be shown in the fowl, the hare or rabbit, the adder 

 or frog, &c. 



A few casts, showing the size and appearance of the human brain, that of the 

 ourang-outang, of idiots, &c., and casts cf the heads of the Carib, Negro, European, 

 &c., form excellent illustrations of this section, and can easily be obtained. 



Appropriate figures for illustrating this section will be found in Fletcher's Rudiments 

 of Physiology, Part I., pages 47 and 48; in Lizars colored plates, pages 64, 67, 68; in 

 Roget's Bridgewater Treatise, vol. ii. pages 547, 550, 552, &c.] 



Front view of a section of the Spinal Cord, and Spinal Nerves 



A Spinal Cord. B Spinal Nerve. C Motor branch of Spinal Nerve, D Ganglion of 

 posterior branch of Spinal Nerve. 



