FATIGUE AND SLEEP HYPNOSIS 949 



nucleus become irregular in outline ox crenated. Later on, and, i1 

 would seem, rather abruptly, swelling of the nucleus and, after some time, 

 of the cytoplasm occurs. This is due to oedema, and may be taken tc 

 indicate an upset of their normal osmotic relations. The earlier occur- 

 rence of oedema in the nucleus leads to another change in the nucleus- 

 plasma relation, which is now disturbed in favour of the nucleus. In the 

 measure in which fatigue progresses the extranuclear chromatic material 

 continues to be used up, and, in spite of its replenishment from the 

 nucleus, it almost or entirely vanishes from the cytoplasm. Then 

 follows what is perhaps a ' last effort ' on the part of the nucleus to 

 supply the cytoplasm, in the form of a discharge of chromatic substance, 

 which first masses itself around the outside of the nuclear membrane, 

 and thence gradually diffuses into the cytoplasm. With the using up 

 of this supply all the basic chromatic material of the cell, except that in 

 the karyosome (nucleolus), is exhausted. Finally, this too is yielded 

 up to the cytoplasm, and with its consumption there remains a totally 

 exhausted cell, devoid of basic chromatin and incapable of recuperation. 

 According to Pugnet, even in extreme fatigue, as when dogs were 

 caused to run forty to nearly sixty miles in a special apparatus, the 

 changes varied greatly in degree in different cortical cells, from mere 

 diminution of the chromatic substance to complete disappearance of it. 

 and such disintegration of the cell as must have precluded its recovery, 

 had the animal been allowed to live. Many, and indeed most, of the 

 cortical cells were quite unaffected. Histological alterations may also 

 be. caused in sympathetic ganglion cells by prolonged artificial stimula- 

 tion of the nerves connected with the ganglia. Experiments on fatigue 

 changes in the cells of the spinal ganglia after electrical excitation of the 

 posterior root-fibres are less decisive, some observers having obtained 

 positive, others negative, results (p. 885). 



Theories of the Causation of Sleep. (i) Some have suggested that sleep 

 is induced by the using up of substances necessary for the functional 

 activity of the neurons e.g., the stored-up or intramolecular oxygen 

 or by the action of the waste products of the tissues, and especially lactic 

 acid, when they accumulate beyond a certain amount in the blood, or in 

 the nervous elements themselves. 



(2) Others have looked for an explanation to vascular changes in the 

 brain, but so far are the possible causes of such changes from being 

 understood, that it is even yet a question whether in sleep the brain is 

 congested or anaemic. Certain writers have settled this question by the 

 summary statement that when the brain rests the quantity of blood in 

 it must be supposed to be diminished, as in other resting organs. But 

 this is a fallacious argument. For when the whole body rests, as it does 

 in sleep, it has as much blood in it as when it works; in sleep, therefore, 

 if some resting organs have less blood than in waking life, other resting 

 organs must have more; and it is the province of experiment to decide 

 which are congested and which anaemic. In coma, a pathological con- 

 dition which in some respects has analogies to profound and long- 

 continued sleep, the brain is congested, and the proper elements of the 

 nervous tissue presumably compressed. And artificial pressure (applied 

 by means of a distensible bag introduced through a trephine hole into 

 the cranial cavity) may cause not only unconsciousness, but absolute 

 anaesthesia. But it is possible that this artificial increase of intra- 

 cranial pressure may produce its effects by rendering the brain anaemic, 

 and it has been actually observed that the retinal vessels, as seen with 

 the ophthalmoscope, and the vessels of the pia mater exposed to direct 

 observation in man by disease of the bones of the skull, or in animals by 

 operation, shrink during sleep. Statements to the contrary may be due 



