448 MR HAROLD AXEL HAIG ON 



The head is at this stage not large in proportion to the trunk ; rudiments 

 of the vibrissae are to be seen at the sides of the snout, and the eyelids are 

 formed although the palpebral fissure is not as yet open. The tongue is an 

 elongated organ, with a cleft tip, the two divisions appearing between the lips in 

 the middle line. 



No sign of an external ear is present, nor is there any opening indicating the 

 position of an auditory meatus. 



The whole trunk is curved towards the ventral aspect, but some of the curvature 

 is probably due to mechanical causes subsequent to removal of the foetus from 

 the uterus. 



Reference to PL I. fig. 1 will render the above points clear. 



SECTION I. 



GENERAL TOPOGRAPHY AND ANATOMY. 

 A. Appearance of the Main Viscera in situ, from the Ventral Aspect. 



A median ventral incision was made, and flaps of skin and deeper tissues turned 

 back to expose the structures in the neck, thorax, and abdomen ; the sternum and 

 ribs being also removed for the purpose of demonstrating the thoracic viscera, whilst 

 the attachments of the diaphragm to the lower ribs were likewise severed. A 

 separate flap was raised in the neck region to expose the larynx, trachea, thyroid, and 

 parathyroids, and finally the parietal pericardium was cut away. 



In the region of the umbilicus, care was taken not to sever the connection of the 

 urinary bladder with the umbilical cord, and the umbilical vein passing from the 

 cord to the liver was also kept intact ; subsequently, however, these connections were 

 severed for greater convenience of examination. 



Reference to fig. 2, Plate L, will show that the heart is at this stage a large 

 organ filling the greater part of the thoracic cavity ; from the ventral aspect, the 

 right ventricle appears larger than the left, and the right auricular appendix wider 

 than the left ; the right appendix has a deep notch in its lower border, whilst the 

 left one possesses three such notches. 



A portion of the aortic trunk shows above and dorsal to the right appendix. 



The thymus is relatively large, and extends from the root of the neck, where it is 

 bifurcated, towards the left of the middle line, until it reaches a point just anterior 

 to the left auricular appendix : the main mass of the thymus is subdivided into a 

 number of lobes and lobules, and there are a few small isolated masses situated at 

 the sides of the trachea just anterior to the upper bifurcated extremity.* 



The lungs lie compressed against the walls of the thorax, and are not very obvious 

 from the ventral aspect, the right upper lobe being most prominent, and below 



* Microscopical examination showed that these isolated masses possessed a typical thymus structure. 



(ROY. soc. KDIN. TRANS., VOL. L., 226.) 



