28 The Physiology of the Corpus Spongiosum, &c. 



fluid, is of interest. During micturition the entire corpus spon- 

 giosum, as well as the urethra, becomes somewhat stretched. At 

 the end of micturition the tonicity of the trellis-work is sufficient 

 to coaptate the walls of the urethra, and to expel the last drops of 

 urine which may remain in the anterior portion of the canal This 

 pressure is strongest at those parts where the urethra and its sur- 

 rounding meshes are narrow ; and weakest where these cavities are 

 wide, and consequently more dilatable, as at the bulb. 



As the external fibrous investment of the corpus cavernosum 

 consists of broad, thick bands of connective tissue, it becomes firmer, 

 harder, and more unyielding during erection, than the corpus spon- 

 giosum. The latter being smaller in circumference, with its external 

 fibrous investment interspersed with non-striped muscular bands, 

 it remains even during the most complete erection, and during the 

 ejaculation of the sperm, sufficiently dilatable or distensible to permit 

 the seminal fluid to flow through the canal. Should the corpus 

 spongiosum attain that degree of hardness which the corpus caver- 

 nosum acquires, the canal would not yield to the pressure of the 

 sperm, and ejaculation would be obstructed. 



The pressure which the corpus spongiosum is capable of exerting 

 upon the urethra becomes quite considerable, when to the natural 

 tonicity of its muscular trellis- work above mentioned there is added 

 a special stimulus to contraction, which obtains when the penis is 

 brought to a state of erection. Each new pulsation increases the 

 quantity of blood in the meshes or venous cavities, and this — as it 

 were — supplementary body within these cavities stimulates the mus- 

 cular bands to increased activity. The pressure now brought to 

 bear by these bands very materially assists the acceleratores urinse 

 and compressor urethrae muscles in communicating an expulsive 

 impetus to the outflowing stream of urine or seminal fluid. 



The greater the special force exerted by the contraction of the 

 acceleratores urinae during ejaculation, the more is the erection of 

 the penis augmented, and the concentrical pressure of the muscular 

 trellis- work upon the spermatic fluid increased. 



For this reason micturition is so difficult during complete erec- 

 tion, and immediately after ejaculation. 



Thus I have endeavoured to lay before you, in a somewhat con- 

 densed form, a synopsis of some views at present entertained upon 

 the histology and physiology of the penis. This subject is but 

 imperfectly understood ; its literature is meagre, and much of that 

 which has been written is vague and unsatisfactory, while many 

 points have remained entirely unexplored. Yet there are few sub- 

 jects which present a more fruitful field for histological investigation 

 than the one to which I have now had the honour of calling your 

 attention. — Read hefore the New York Dermatological Society. 



