MINUTE ANATOMY OF THE OMENTUM. 243 



Ranvier's description of the mode of the formation of blood- 

 vessels in these patches varies somewhat from that described 

 by myself. After a new investigation of the development of 

 blood-vessels in similar patches of the omentum of very young 

 guinea pigs, 1 have come to the conclusion that the mode of 

 development of blood-vessels in the young animal corresponds 

 to that described by me of those in the rabbit and not to that 

 maintained by Ranvier. If a preparation be prepared in the 

 above manner (2 percent, bichrom. of potash for eight to ten 

 days, washing in water and then staining in haematoxylin or 

 carmine and haematoxylin) from the omentum of a young 

 guinea-pig (not older than three or four weeks) and the vicinity 

 of large vessels be examined, numerous places may be sought 

 out in which a development of new blood-capillaries can be 

 easily discovered. 



Fig. 8 accompanying this paper is taken from such a part. 

 In this figure there are two capillary vessels which are still 

 in a young condition; they still show the cells by whose 

 vacuolation and fusion the vessel has been formed. In close 

 vicinity to the vessels we find very numerous cells, the 

 greater number of which are vacuolated in various ways, as 

 is shown in the figure. These vacuolated cells have a more 

 or less distinct linear arrangement, and we have only to 

 imagine that those parts by which they are in contact become 

 absorbed or disappear, to obtain a portion of a capillary 

 vessel. Although the number of vacuolated cells is smaller 

 in most patches where the development of blood-vessels has 

 begun, than that represented in figure 8, still it is so large in 

 my specimens that their importance for the development of 

 blood-vessels cannot be overlooked. Besides, the condition 

 and aspect of the young capillaries like those represented in 

 fig. 8 strongly support the view just mentioned. 



To say that the vacuolated cells and the above condition 

 of the young capillaries is due to the influence of the reagent 

 used (2 per cent, solution of bichromate of potash), would 

 be against all our experience of the action of that fluid. 

 From the foregoing we see that vacuolation is important for 

 the origin of the holes at the fenestrated omentum in general 

 and also for the development of capillary vessels in the patches 

 and nodules, in the omentum of the young guinea pig ; in 

 the former case the vacuolation takes place in the interstitial 

 substance of the connective-tissue stroma, in the latter case 

 in the cells of the matrix ; and by fusion of the vacuolated 

 cells capillary vessels are formed. 



The omentum of the above case has not been fenestrated 

 yet ; it contained only indications of it in the form of a few 



