196 THE CIRCULATION. 



probably, at the same time arrives in greater quantity, 

 owing to a simultaneous dilatation of the arteries of the 

 parts, and thus the plexuses become filled, and remain so 

 until the stimulus to erection subsides, when the organic 

 muscular fibres again contract, and so gradually expel the 

 excess of blood from the previously distended vessels. 

 The influence of cold in producing extreme contraction and 

 shrinking of erectile organs, and the opposite effect of 

 warmth in inducing fulness and distension of these parts, 

 are among the arguments used by Kolliker in support of 

 this opinion. 



The accurate dissections and experiments of Kobelt, 

 extending and confirming those of Le Gros Clark and 

 Krause, have shown, that this influx of the blood, however 

 explained, is the first condition necessary for erection, and 

 that through it alone much enlargement and turgescence 

 of the penis may ensue. But the erection is probably 

 not complete, nor maintained for any time except when, 

 together with this influx, the muscles already mentioned 

 contract, and by compressing the veins, stop the efflux of 

 blood, or prevent it from being as great as the influx. 



It appears to be only the most perfect kind of erection 

 that needs the help of muscles to compress the veins ; and 

 none such can materially assist the erection of the nipples, 

 or that amount of turgescence, just falling short of erec- 

 tion, of which the spleen and many other parts are capable. 

 For such turgescence nothing more seems necessary than 

 a large plexiform arrangement of the veins, and such 

 arteries as may admit, upon local occasions, augmented 

 quantities of blood. 



