perinaeal fascia, the structures between its layers, and the anterior fibres of K, the levator ani muscle. The incision, if made in due reference to the relative situation of the parts above noticed, will leave them untouched; but when the pudic artery, or some one of its branches, deviates from its ordinary course and crosses the line of incision, a serious haemorrhage will ensue, despite the anatomical knowledge of the most experienced operator. When it is requisite to divide the superficial and deep sphincter ani as in the operation for complete fistula in ano, if the incision be made transversely in the ischio-rectal fossa, the haemorrhoidal arteries and nerves converging towards the anus will be the more likely to escape being wounded. DESCRIPTION OF THE FIGURES OF PLATES 50 & 51. PLATE 50. FIGURE 1. A. The umbilicus. B. The linea alba. C. The suspensory ligament of the penis. D D. The two corpora cavernosa penis. E E**. The hypogastric and scrotal superficial fascia. F F. The spermatic cords. FIGURE 2. A. The umbilicus. B. The urethra. C*. The tunica vaginalis; c, the testicle invested by the tunic. D D. The corpora cavernosa seen in section. E. The scrotal raphe and septum scroti. FIGURE 3. A B. The perinaeal raphe. C. The place of the coccyx. D D. The projections of the ischiatic tuberosities. BE. The line of section in lithotomy. [Illustration: Legs and scrotum, showing bone, blood vessels and other internal organs.] Plate 50; Figure 2, Figure 3, Figure 1. PLATE 51. FIGURE 1. A. The superficial fascia covering the urethral space. B. The sphincter ani. C. The coccyx. D D. The right and left ischiatic tuberosities. H. The anus. I I. The glutei muscles. FIGURE 2. A, B, C, D, H, I. The same parts as in Fig. 1. E. The accelerator urinae muscle. F F. Right and left erector penis muscle. G G. Right and left transverse muscle. [Illustration: Abdomen, showing bone, blood vessels and other internal organs.] Plate 51; Figure 2, Figure 1. COMMENTARY ON PLATES 52 & 53. THE SURGICAL DISSECTION OF THE DEEP STRUCTURES OF THE MALE PERINAEUM. THE LATERAL OPERATION OF LITHOTOMY. The urethra, at its membranous part, M, Fig. 1, Plate 53, which commences behind the bulb, perforates the centre of the deep perinaeal fascia, E E, at about an inch and a half in front of F, the anus. The anterior layer of the fascia is continued forwards over the bulb, whilst the posterior layer is reflected backwards over the prostate gland.