498 ARTHUR WILLIAM MEYER 



supposition which would, however, fail to explain the early 

 fibrous transformation above mentioned. Moreover, the sur- 

 prising fluctuations in the duration of pregnancy which have 

 been observed would seem to make the occurrence of pre-natal 

 degenerative changes not impossible. 



In another dog but 45 hours old the conditions were quite 

 different for the lumen of the vein which was patent contained 

 uncoagulated blood except in the immediate neighborhood of 

 the umbilicus. Nevertheless, degenerative changes had already 

 appeared and were particularly evident in the musculature es- 

 pecially immediately beneath, i.e., external to the endothelium. 

 The cell outlines were lost and the media was represented by a 

 uniformly ill-preserved syncytial mass which easily took an 

 acidophile stain. The nuclei were very large, vesicular, and 

 irregular in outline and arrangement. The intima was quite 

 well preserved in most places but in others the cells which were 

 irregular in form had become elongated, the nuclei were large 

 and swollen and large vascuoles were found between and es- 

 pecially below the cells of the intima. The most striking thing, 

 however, is the occurrence of projections of club-shaped proc- 

 esses into the lumen as represented in figures 9 and 10. In the 

 case of figure 9 this projection was still capped by the de- 

 generating endothelial cells on which erythrocytes lay. The 

 same is true of the similar though larger and longer projection 

 represented in figure 10 which is taken from the same vessel 

 somewhat farther peripherally. In this case the elongation 

 and vacuo lation of the endothelial cells some of which have 

 been cast off, are well seen but the honey-combed process is still 

 capped by some of them. 



Since no series of vessels taken from pups only several hcjurs 

 apart in age were examined it is impossible to say whether this 

 process formation is a constant phenomenon in the degenerating 

 vein in the dog. It was not observed in the sheep and before 

 discussing the significance of these facts I desire to call attention 

 to changes observed in the hypogastric arteries and the omphalo- 

 mesenteric veins. In case of two of the latter which were still 

 attached to the abdominal wall in a dog 91 hours old similar 



