278 ANNUAL OF SCIENTIFIC DISCOVERY. 



the condition of the water of the body. By cold the water is 

 changed from a liquid to a solid state. Nerve tissue contains 85 

 per cent, of water. If we make this water solid, we get all the 

 phenomena of negation demonstrated, — a sort of temporary 

 death. These phenomena may also be produced by heat or the 

 action of alcohol ; so that, by congehition on the one hand, and 

 by coagulation or desiccation on the other, we get precisely the 

 same phenomena. 



One of the most striking results of expeviments on animals in 

 this direction is the local independence of the several portions of 

 the nervous system ; every part seems to have its own centre, so 

 that many parts of the cerebrum may be isolated. We may act 

 on one hemisphere, or both, or on the cerebellum, or on the me- 

 dulla oblongata, or spinal cord ; but we do not thereby necessa- 

 rily interfere with the functions of the other parts of the nervous 

 system. This fact explains many points in connection with dis- 

 eases of the brain. There is, nevertheless, to be noticed a kind 

 of balance on one part by another; one hemisphere evidently 

 balances the other; the corpora striata balance, and are balanced 

 by, the cerebellum ; the medulla is in the same relation with some 

 part not yet precisely determined. One part of the medulla 

 balances a part of the spinal cord connected with respiration, — 

 the former presiding over the inspiratory muscles, the latter over 

 those of expiration. If we freeze the medulla we stop the breath- 

 ing by arresting inspiration; if we freeze the balancing portion 

 of the cord we arrest the expiratory act. Thus, in the nervous 

 functions there is a balance of opposite powers, just as in the 

 muscular S3'stem there is a balance of flexors and extensors. The 

 interest of this in a pathological point of view is evident. 



Psychologically, also, these experiments are interesting, as, 

 for instance, in tae act of going to sleep in the upright position ; 

 sleep begins in the visual organs apparently ; as the anterior part 

 of the brain first loses its power, the tendency is to nod, to fall 

 forward, caused by that part becoming inactive, while the posterior 

 parts retain their function of propelling. The same may perhaps 

 be said of the shock which sometimes results from looking down 

 great heights; the shock paralyzes the anterior or thinking part, 

 and the cerebellum retains its power and so gives an impulse for- 

 ward. One bird shot flying will fall at once, rolling over and 

 over forward, while another turns over many times backward in 

 its descent. Dr. Richardson believes that in the former case the 

 bird will invariably be fcnmd shot through the cerebrum, and in 

 the latter throuo:h the cerebellum. 



When the process of sudden freezing is brought to bear on the 

 whole cerebro-spinal system of a cold-blooded animal, as a frog, 

 every function of life is immediately suspended ; it seems a hard 

 frozen mass, and is apparently dead, j'et it only sleeps. If heat 

 be taken up by it from the surrounding air, it recovers b}' degrees, 

 and awakes without injur3^ By the freezing we have fixed all 

 the water of its tissues, have stopped evaporation, suspended 

 motion, and arrested waste; but we have done no injury that 

 ma}- not be removed by the re-solution of the water and bj" the 



