ANATOMY OF A MONODACTYLOUS FOETUS 425 



carried out in the distal part of the evagination from the trunk 

 of the body, being drawn out later only in the proximal part of 

 the limb, so that a complete upper arm is formed but only the 

 radial half of the rest of the limb. Secondly, these segments 

 may have been drawn out, the limb bud being normal, but fur- 

 ther differentiation not occurring, so that what is seen in the 

 limb represents a fused radius and ulna in the forearm, fused 

 carpals and digits in the hand. The arguments against the 

 digit really representing all five have already been reviewed, 

 and against the view of the ulna being included in the forearm 

 is the absolutely typical shape and size of the radius, the dis- 

 tribution of nerves and muscles, and the appearance on the 

 right arm of a digit at the elbow, as if this point represented the 

 distal end of the ulnar portion of the arm. Thirdly, the limb 

 bud again may have been normal, without fusion of the radial 

 and ulnar anlagen in the skeleton, only the radial half going on 

 with its development, the ulnar half failing entirely, except for 

 the digit at the right elbow. The presence of this digit lends 

 color to this third view. 



DIAPHRAGMATIC HERNIA 



After the rest of this paper was written, out of curiosity 

 aroused by the flatness of the abdomen, I opened the body 

 cavity to examine the viscera, and was surprised to discover a 

 diaphragmatic hernia with a large proportion of the abdominal 

 viscera situated in the left pleural cavity. The right half of the 

 diaphragm was intact and perfect, but the left half was almost 

 entirely absent. The sternal and vertebral regions were present 

 and joined in the central tendon, forming a free edge to the dia- 

 phragm in the midsagittal plane. The left costal origin was 

 indicated in front by a muscular ridge 2 to 3 mm. high following 

 the costal margin as far back as the axillary line and the whole 

 of the left half of the diaphragm except this narrow peripheral 

 band was absent, leaving a wide open communication between 

 the pleural and peritoneal cavities. The left mediastinal pleura 

 passed over the medial free edge of the opening to become dia- 

 phragmatic peritoneum under the right half of the diaphragm, 



