PHYSIOLOGICAL 253 



expressions of grief are undoubted, but these are not associated 

 with tears. The fact that weeping seems to require some practice in 

 young children is in harmony with Darwin's conclusion that the 

 habit "must have been acquired since the period when men branched 

 off from the common progenitor of the genus Homo and of the non- 

 weeping anthropomorphous apes". 



Some races weep much more readily than others, as may be 

 noticed among sailors and soldiers under very severe exposure, but 

 this is an intricate question. The more emotionalised types will 

 tend to weep more readily, but this may be counteracted by 

 habituated control. 



According to Darwin, the origin of weeping in the individual 

 child is to be found in the gorging of the blood-vessels of the eye 

 as the result of prolonged screaming, this being due to pain or 

 hunger or the like. The gorging of the blood-vessels of the eye is 

 associated with a contraction of the surrounding muscles and with 

 other effects which react reflexly on the lachrymal glands and 

 induce exaggerated secretion of tears. 



On this view, crying is primary, and weeping is a secondary con- 

 sequence. It is not of great physiological use, perhaps, for it is not 

 without justification that we speak of "idle tears"; and yet it has 

 been racially justified as a safety-valve which lessens congestion 

 and may actually relieve pain. In all probability, however, the 

 biology of tears requires another chapter, which will disclose the 

 influence of some hormone, such as adrenalin, which has such a 

 notable influence on the tone of the muscles, the blood-pressure, 

 the breathing-movements, and so forth. It is well known that an 

 extra supply of adrenalin follows an emotional storm, like that of 

 anger. The sympathetic nervous system is excited; the thrill passes 

 to the suprarenal bodies; more adrenalin is produced and rapidly 

 distributed throughout the body by the blood stream. We know 

 that the cat's hair stands on end automatically in an emotional 

 gust induced by an obtrusive dog : so it may be that our tears have 

 a similar emotional-endocrinal factor. 



THE HEARING EAR.— It is usual and convenient to consider the 

 organ of hearing under three heads: the outer ear, the middle ear, 

 and the inner ear. The first two are simple enough; but the inner 

 ear is a complicated system of tubes and bulbs and canals, appro- 

 priately called the labyrinth. But the greater part of the labyrinth 

 has to do with the sense of balance, and not with hearing at all; it 

 is not to be considered under this heading. 



To understand the organ of hearing at all, it is necessary to 

 understand the nature of sound, which is a vibration transmitted 

 by molecules, usually in the air, but equally well in water or in 

 solids. When a taut violin-string is plucked, it emits a note; that 



