1384 



THE URINO GENITAL ORGANS 



The head is oval, but flattened so that when viewed in profile it is pear-shaped. 

 Its anterior part is covered by a layer of modified tissue called the head-cap or 



perforator. 



The neck and body together form a cylindric or rod-like segment, the neck 

 containing the two centrosomes. From the posterior centrosome proceeds the 

 axial filament, which in the body of the spermium is encircled by a spiral thread. 



The tail is about four times the combined length of the head and body, and 

 consists of the axial filament surrounded by a delicate sheath of protoplasm. 

 The terminal portion of the tail is named the end piece, and consists of the axial 

 filament only. 



By virtue of their tails, which act as propellers, the spermia, in the fresh con- 

 dition, are capable of free movement, and if placed in favorable surroundings 

 (e. g., in the female passages) may retain their vitality for several days. 



.Head 



Head* 



Middle . 

 piece 



' Main piece 



of 

 the 

 tail 



Applied Anatomy. The scrotum forms an admirable 

 covering for the protection of the testicle. This body, lying 

 suspended and loose in the cavity of the scrotum, and sur- 

 rounded by a serous membrane, is capable of great mobility, 

 and can therefore easily slip about within the scrotum, and 

 thus avoid injuries from blows or squeezes. The skin of the 

 scrotum is very elastic and capable of great distention, and 

 on account of the looseness and amount of subcutaneous 

 tissue, the scrotum becomes greatly enlarged in cases of 

 edema, to which this part is especially liable on account of 

 its dependent position. The scrotum is frequently the seat 

 of epithelioma; this is no doubt due to the rugse on its surface, 

 which favor the lodgement of dirt, and this, causing irritation, 

 is the exciting cause of the disease. Cancer was especially 

 common in chimney-sweeps from the lodgement of soot. 

 The scrotum is also the part most frequently affected by 

 elephantiasis. 



On account of the looseness of the subcutaneous tissue 

 considerable extravasations of blood may take place from very 

 slight injuries. It is therefore generally recommended never 

 to apply leeches to the scrotum, since they may lead to 

 considerable ecchymosis, but rather to puncture one or more 

 of the superficial veins of the scrotum in cases where local 

 bloodletting from this part is judged to be desirable. The 

 muscle fibre in the dartos causes contraction and consider- 

 able diminution in the size of a wound of the scrotum, as 

 after the operation of castration, and is of assistance in keep- 

 ing the edges together and covering the exposed parts. 

 Abnormalities in the formation and in the descent of the testes may occur. The testis may 

 fail to be developed, or it may be fully developed and the vas deferens may be undeveloped in 

 whole or in part; or, again, both testes and vas deferens may be fully developed, but the duct may 

 not become connected to the gland. The testis may fail in its descent (cryptorchismus) or it may 

 descend into some abnormal position (ectopia testis). Thus, it may be retained in the position 

 where it was primarily developed, below the kidney; or it may descend to the internal abdominal 

 ring, but fail to pass through this opening; it may be retained in the inguinal canal, which is, 

 perhaps, the most common position; or it may pass through the external abdominal ring and 

 remain just outside it, failing to pass to the bottom of the scrotum. On the other hand, it may 

 get into some abnormal position; it may pass the scrotum and reach the perineum, or it may 

 fail to enter the inguinal canal, and may find its way through the femoral ring into the crural 

 canal, and present itself on the thigh at the sapheneus opening. Ectopia testis is due to the 

 absence, overdevelopment, or malposition of some portion of the gubernaculum. There is still 

 a third class of cases of abnormality in the position of the testis, where the organ has descended in 

 due course into the scrotum, but is malplaced. The most common form of this is where the testis 

 is inverted; that is to say, the organ is rotated, so that the epididymis is connected to the front of 

 the scrotum, and the body, surrounded by the tunica vaginalis, is directed backward. In these 

 cases the vas deferens is to be felt in the front of the cord. The condition is of importance in 

 connection with hydrocele and hematocele, and the position of the testis should always be care- 

 fully ascertained before performing any operation for these affections. Again, more rarely, the 

 testis may be reversed. This is a condition in which the top of the testis, indicated by the globus 



piece J 



FIG. 1135. Spermium of man. At 

 the left a surface view is shown; 

 at the right a lateral view. X 1200. 

 (Szymonowicz, after Retzius.) 



