September 2, 1887.] 



SCIENCE. 



115 



At the time well ventilated. Besides, the quantity of chloroform 

 necessary to saturate the air sufficiently to produce anaesthesia is 

 very considerable. Allowing one and a half grain of chloroform to 

 the cubic inch of air, it would require thirty-eight fluid ounces to 

 sufficiently impregnate the air of a room ten by twelve feet, with a 

 ceiling eight feet high. It would certainly take a considerable time 

 to vaporize this quantity of chloroform, to say nothing of the 

 probability of awakening sleepers by any act of atomization, and 

 even if it should succeed, what would be the effect on the burglars 

 themselves? 



MENTAL SCIENCE. 

 Why do we Sleep ? 



In an address to the Anthropological Society of Brussels, Prof. 

 Leo Errera has given a 7-hunu' of some points in the chemical 

 theory of sleep. The phenomena of sleep have in common with 

 other vital functions the character of periodicity. An examination 

 of such periodic functions in general may aid in ascertaining the 

 cause of sleep. The respiratory rhythm is regulated by the amount 

 of o.\ygen and carbonic acid in the arterial blood. When the blood 

 is charged with oxygen the respirator)' centre momentarily sus- 

 pends activity ; but soon the tissues yield their oxygen to the blood, 

 have it replaced by carbonic acid, and the blood thus modified acts 

 as an excitant to the respiratory centre. Ranke has shown that the 

 fatigue and recovery of muscles is due to a similar alternation of 

 the accumulation and discharge of certain ' fatiguing substances,' 

 chief amongst which is lactic acid. An injection of this acid into 

 fresh muscle renders it incapable of work ; washing the acid out 

 restores the activity. Cannot sleep be explained by a similar chem- 

 ical theory ? Preyer has extended the views of Binz, Obersteiner, 

 and others (who all agree in making the accumulation of certain 

 products of fatigue — ermudungsstoffe — the cause of sleep), by 

 calling all such fatiguing products of activity ' ponogens.' These 

 accumulate in waking life, are readily oxidizable, and absorb the 

 oxygen intended for glands, muscles, and nerve-centres, until action 

 is impossible and sleep sets in. Gradually the ponogens are de- 

 stroyed by oxidation, slight excitation is sufficient to arouse the 

 centres, and waking life begins. Amongst the ponogens, Preyer 

 counts lactic acid as the chief, but the experimental demonstration 

 of this has been unsuccessful, and the theor)', accordingly, not gen- 

 erally adopted. 



Since these researches Armand Gautier has found in the human 

 body a series of five organic bases akin to creatine, creatinine, and 

 xanthine, and calls them ' leucomaines ' and ' ptomaines.' The 

 physiological properties of these substances are narcotic, fatiguing, 

 and sometimes lead to vomiting. This is just what the chemical 

 theory requires. The periodicity of sleep would be explained by 

 the conservation of energy being applicable to all bodily activity : 

 work must be followed by repair ; life is a slow suicide. There is, 

 moreover, reason to believe that the action of these leucomaines is 

 a direct one upon the brain ; it is a direct intoxication of the brain- 

 centres. 



A theory of sleep must take account of three factors, work, 

 fatigue, and sleep. The chemical theory satisfies these demands. 

 All work, muscular or cerebral, produces waste products. These 

 accumulate, make work more and more difficult : this is fatigue. 

 As the process continues, the waste-products, notably the leuco- 

 maines, intoxicate the higher nerve-centres (just as a dose of mor- 

 phine does), and render them incapable of action : that is sleep. 

 The picture is, however, much more complex. There is a constant 

 struggle against the fatigue, which for a time, by dint of hard work 

 shown in increased secretions and so on, may succeed. We proba- 

 bly never arrive at the extreme limit of work ; the sensation of fa- 

 tigue intervenes to prevent such a disaster. Fatigue, as is well 

 known, may extend from muscle to nerve, and from nerve to nerve- 

 centre. We may be veiy tired from repeatedly lifting a weight, and 

 not be sleepy, and may be generally sleepy without any considera- 

 ble local fatigue. One is peripheral, the other central. As the 

 waste products accumulate in the centres, motion and sensation be- 

 come more and more sluggish until the time comes when the or- 

 dinaiy stimulation no longer arouses them, and we sleep. Partial 

 sleep can be similarly explained. The centres go to sleep in a 

 hierarchical order, the highest serving the most delicate function 



going first. In waking, the reverse is the case ; the motor centres 

 may be asleep while the intellectual centres are awake. In som- 

 nambulism the latter may be asleep while the former are awake. 



The depth of sleep according to this theory ought to be propor- 

 tional to the number of cortical molecules in combination with the 

 leucomaines. In the beginning of sleep these are abundant, the 

 cerebral cells inactive, and a combination easy. The sleep is deep. 

 Soon the maximum number of combinations is reached, and sleep is 

 deepest. From here on, the leucomaines are gradually eliminated 

 and destroyed, and sleep should decrease with a decreasing in- 

 tensity. Kohlschiitter's experiments on the intensity of sleep, as 

 tested by the noise necessary to awake the patient, gives the curve 

 for the intensity of sleep corresponding to what we should expect by 

 our theory. Variations in our sleep caused by an excess of work, 

 etc., are evidently similarly explicable. In short, fatigue is a poison 

 for which sleep is the normal antidote. 



This theory maintains (i) that the activity of all the tissues (and 

 primarily of the two most active, the nervous and muscular) gives 

 rise to substances, more or less allied to alkaloids, the leucomaines ; 

 (2) that these induce fatigue and sleep ; (3) that on waking, if the 

 body is rested, these substances have disappeared. 



To complete the demonstration of these statements much careful 

 experimentation is necessary ; but the facts as far as they go make 

 it probable that the chemical theory of sleep will gain in strength 

 as our knowledge advances. 



ETHNOLOGICAL NOTES. 



The Hawaiian Islands. — Dr. E. Arning's researches have been 

 very successful. He was sent there by the curators of the Hum- 

 boldt Fund at Berlin, in order to study leprosy, which has recently 

 become the plague of the natives of this group. He stayed there 

 for two and a half years, and during this time carefully collected 

 relics of the ancient Hawaiian culture, and succeeded in bringing to 

 light many points of interest, thus proving that European influence, 

 which has swamped the islands since 1820, has not totally de- 

 stroyed the remembrance of olden times. When the missionaries es- 

 tablished their schools in Hawaii, the natives rapidly adopted Euro- 

 pean customs, burnt their temples and idols, and cast the stone 

 images of their deities into the sea. The destruction was so complete 

 that no traces seemed to remain. Arning, in studying the disease 

 mentioned, had ample opportunities to come into contact with the 

 natives in the remote villages of the islands, and here he found still 

 many relics, and received information about the ancient arts and 

 customs. His notes on the fishery of the Hawaiians are of interest. 

 They were skilful divers, and used to frighten the fishes out of the 

 caVes and hollows of the rocky ground with sticks, and then catch 

 them in nets. When fishing in the canoe, they used a sacred piece 

 of heavy wood, called melomelo, which was kept in the sacred part 

 of the hut, and was placed, with many ceremonies, in the canoe. 

 It was attached to the net in order to attract the fish by its magic 

 spells. A variety of hooks were used for different kinds of fish and 

 according to the time of day, irisated shells being applied at noon and 

 in a bright sun, while white ones served early in the morning and 

 late in the evening. Arning describes their games, the wooden 

 sledges on which they used to glide down the steep slopes of the 

 mountains ; the remarkable boards of koa-wood, shaped like an iron- 

 ing board, standing on which they rode through the surf ; the jnoa, 

 a spindle-shaped piece of heavy wood, the use of which was allowed 

 to the chiefs alone, who let it glide down the slope of a hill, at the 

 foot of which it had to pass between two poles ; and the famous 

 game of maika, which is similar to the Italian ' boccia.' At the 

 present time, when a powerful reaction against the missionaries is 

 spreading all over the islands, the old hicla dance has been revived, 

 and the ancient dancing, ornaments, and musical instruments 

 are used again. Aming describes a foot ornament made of 960 

 canine teeth of dogs, the work of several generations, — for dogs 

 were slaughtered only at high festivals, — their drums, flutes, and 

 xylophones. Arning's observations and collections form one of the 

 most important recent contributions to Polynesian ethnology, and 

 are the more valuable as they were made in a country which 

 seemed to have lost all its originality by its rapid commercial de- 

 velopment. 



