153. =Metacarpal joint of thumb.=--The joint of the metacarpal bone of the thumb with the trapezium can be distinctly felt by tracing the dorsal surface of the bone upwards till we come to the prominence which indicates the joint at the bottom of the ‘tabatière anatomique’ (144). Supposing, however, there be much swelling, the knife introduced at the angle between the first and second metacarpal bones readily finds the joint if the blade be directed outwards. 154. =Sesamoid bones.=--The sesamoid bones of the thumb can be distinctly felt. Just above them--that is, nearer to the wrist--lies the joint between the metacarpal bone and the first phalanx. We should remember the position of these bones in amputation at this joint. _Mutatis mutandis_ the same observations apply to the sesamoid bones of the great toe. The extensor tendon of the last joint of the thumb crosses the apex of the first interosseous space. Under the tendon, and in the angle between the bones, we feel the radial artery just before it sinks into the palm. 155. =Subcutaneous veins.=--The veins on the back of the hand, and their arrangement in the form of arches which receive the digital veins, is sufficiently obvious. The number and arrangement of the arches may vary, but in all hands it is interesting to notice that the veins from the fingers run up between the knuckles and are out of harm’s way. 156. =Interosseous arteries.=--Since the dorsal interosseous arteries, like the palmar, run along the interosseous spaces, incisions to let out pus should always be made along the lines of the metacarpal bones. 157. =Digital bursæ.=--Small subcutaneous bursæ are sometimes developed over the knuckles and the backs of the joints of the fingers. They often become enlarged and unseemly in persons of a rheumatic or gouty tendency. 158. =Knuckles and digital joints.=--The three rows of projections called ‘the knuckles’ are formed by the proximal bones of the several joints: thus the first row is formed by the ends of the metacarpals; the second by the ends of the first phalanges, and so forth. In amputations of the fingers it is well to remember that in all cases the line of the joints is a little in advance of the knuckles, that is, nearer the end of the fingers. Long and graceful fingers, coupled with thickness and breadth of the sentient pulp at their ends, and too great arching of the nails, have been regarded, ever since the days of Hippocrates, as not unlikely indications of a tendency to pulmonary disease. _PALPATION BY THE RECTUM._ The following report is from Mr. Walsham, of St. Bartholomew’s Hospital, who, having a small hand (somewhat less than seven and a half inches round), has had opportunities of introducing it up the rectum, in the living subject, for the purpose of diagnosis:-- ‘It is possible to introduce the hand (if small) into the rectum; in many cases into the sigmoid flexure, and in rare instances into the descending colon.