( 405 ) 

 EXPLANATION OF PLATES VIII. AND IX. 



(Both Plates are copied from Erdl, " Enticickelung des Henschen." ll ) 

 PLATE VIII. FIG. 1. A human embryo of nine weeks, taken out from the 

 egg -membranes and magnified three times. (Erdl, Plate XII. Pig. 1-5.) 

 The skull is still quite transparent, so that the different divisions of the 

 brain show through : the large mid-brain (" four-bulbs ") is separated from 

 the scarcely larger fore-brain (cerebrum) by a shallow groove, but from the 

 smaller hind-brain (cerebellum) by a deep indentation. The forehead is 

 much arched in front ; the nose is yet very undeveloped; the eye is still dis- 

 proportionately large and wide open. The upper lip is still very short and 

 thickly swollen ; the under lip is very thin ; the chin is short and very re- 

 treating. The whole face is very small in proportion to the skull. The ear- 

 shell is also very small, but the outer opening of the ear very large. The 

 neck is still very short ; the trunk, only about a third longer than the head, 

 is of uniform thickness, and, towards the tail, is produced into a blunt point. 

 The two pairs of limbs are already completely articulated. The anterior 

 limbs (arms) are somewhat shorter than the posterior limbs. The upper 

 and lower parts of the arm (arm and fore-arm) are very short in proportion 

 to the hand, and, similarly, the upper and lower parts of the leg (thigh-bone 

 and leg-bone) are short in proportion to the foot. The fingers on the hand 

 are almost complete; while, on the contrary, the toes on the foot are 

 completely bound, as far as the points, in a swimming membrane, so that 

 they form fins. 



PLATE VIII. FIG. 2. A human embryo of twelve weeks, within the egg- 

 membranes ; natural size. (Erdl, Plate XI. Fig. 2.) The embryo is com- 

 pletely enclosed in the amnion, which is filled with the amnion fluid, as in a 

 water-bath. The navel cord, which passes from the navel of the embryo to 

 the chorion, is sheathed in a continuation of the amnion, which forms folds 

 at the point where it is fastened. Above, the closely-crowded and branched 

 chorion-tufts form the placenta. The lower part of the chorion (cut open 

 and laid in many small folds) is smooth and destitute of tufts. Below it, 

 the "decidna," which is also cut and spread out, is still hanging in deeper 

 folds. The head and limbs of the embryo are already considerably more 

 developed than in Fig. 1. 



PLATE IX. A human embryo of five months ; natural size. (Erdl, Plate 

 XIV.) The embryo is enclosed in the delicate transparent amnion, which 

 has been cut open in front, so that the face and limbs are plainly seen 

 through the opening. The back is bent, the limbs drawn together, so that 

 the embryo occupies the smallest possible space in the egg-cavity. The 

 eyelids are closed. From the navel the thick navel-cord passes, in ser- 

 pentine folds, over the right shoulder to the back, and from there to the 

 spongy placenta (below, on the right). The outer, thin, much-folded cover- 

 ing is the outer egg-membrane, the chorion. 110 



