THE ABDOMINAL WALL 233 



development, and at that time its cavity was continuous with 

 the cavity of the peritoneum. In the later stages of intra- 

 uterine life the upper part of the process is obliterated, 

 and the lower part remains as the tunica vaginalis, which 

 surrounds the testicle everywhere except along its posterior 

 border. 



From the above description the student will understand 

 that there is only one tunic common to both testes, viz., the 

 integument; that the superficial fascia and dartos, forming 

 the dartos tunic, and the investments derived from the 

 abdominal wall, constitute special tunics for each testis. 



Dissection. In cases of old inguinal herniae where the various 

 layers covering the spermatic cord have become thickened, they 

 can be separated and displayed to advantage, but in an ordinary 

 case the student will find that whilst the skin, the dartos, and the 

 tunica vaginalis are readily identified, the external spermatic 

 fascia, the cremasteric fascia, and the internal spermatic fascia 

 are less easily defined, and a satisfactory demonstration of them 

 is difficult. Nevertheless the attempt should be made, and if 

 the steps to be described are followed an excellent demonstration 

 of the constituent parts of the spermatic cord will be obtained. 



On the left side make an incision through the skin of the 

 antero -lateral aspect of the scrotum, from the region of the 

 subcutaneous inguinal ring to the lower end of the scrotum; 

 then reflect the medial part of the divided skin towards the 

 median plane. Remember that the superficial fibres of the 

 dartos are attached to the skin, and therefore keep the edge of the 

 scalpel playing strictly against the skin as the reflection proceeds. 

 Carry the reflection beyond the median plane to demonstrate the 

 fact that the skin forms a common sheath for both testicles, and 

 does not send a deep lamella between them. When the skin is 

 reflected the yellowish-pink layer of dartos tissue is obvious. 

 Make an incision through it similar to the incision through the 

 skin and reflect the medial part towards the median plane. As 

 the median plane is reached a layer of the deep part of the dartos 

 will be found extending upwards as a septum between the 

 testicles. The dartos therefore forms a covering for each testicle, 

 but the covering is incomplete, for the septum of the dartos is 

 incomplete above. The layer of somewhat loose areolar tissue 

 exposed by the reflection of the dartos is the external spermatic 

 fascia. With the handle of the scalpel and the fingers separate 

 it from the deep surface of the dartos. Begin the separation at 

 the lower end of the scrotum and proceed upwards to the sub- 

 cutaneous inguinal ring. When the separation is completed, 

 the testicle and the spermatic cord with their remaining coverings 

 are free. Examine now the extra-peritoneal fatty tissue which lies 

 behind the abdominal inguinal ring. Note that a process of this 

 tissue is prolonged downwards with the cord. Now, with the 

 handle of the knife, gently separate the extra-peritoneal fat from 

 the subjacent peritoneum. Behind the abdominal inguinal ring 

 the peritoneum shows a slight bulging forwards, and a slender 

 fibrous band may be detected passing into the cord from the most 



