EXTRACT XLII, 



ON THE PHYSIOLOGICAL NATURE AND IMPORT OF 

 THE ACTIONS OF YAWNING, STRETCHING, AND 

 SNEEZING, ETC. 



YAWNING, explained by the lexicographer, " is the act 

 of opening the mouth from drowsiness," and so it has 

 been shortly described since the English language was 

 evolved from its original elements. No doubt, if we 

 could penetrate the mists that surround the early history 

 of our race, we could get glimpses of the fact that it 

 has always held a place in the list of human enjoyments and 

 sorrows, and we can plainly see it amongst our domestic 

 friends, both canine and feline, and in the various grades 

 of our nearer relatives, the quadrumana. 



We thus observe that it is one of the most widespread, 

 and, at the same time it may be said, one of the least 

 heeded of our everyday, oft-repeated, involuntary, or 

 automatic acts. 



The act, when patiently analysed, is found to be a very 

 elaborate and complex one. 



The complete and unmitigated yawn may be described 

 as follows: First the disposition to yawn becomes over- 

 powering, then the chest is completely filled by a deep 

 inspiration, the mouth is opened to its full extent, and 

 (when not combined with the general act of ''stretching ") 

 the muscles effecting these movements are relaxed quickly, 

 or more slowly, which event is at once followed by the 

 more or less vigorous contraction of the opposing sets 

 of muscles, with the result that the various local gland 

 structures, but mainly the lachrymal, tonsillar, and salivary,. 



