214 DR. R. KLEIN. 



holes, as described in paragraph 2. If the omentum be 

 already fenestrated, the vacuolated cells become very few, 

 although development of capillary vessels is still going on. 

 I refer to the examination of the omentum of a guinea pig 

 about six weeks old, which omentum is abundantly fenes- 

 trated, almost like that of an adult animal. Although I do not 

 see here any such conspicuous appearances of vacuolated cells 

 near the capillary blood-vessels, as in the former case, still 

 there are capillary vessels to be met with in small patches, 

 the wall of which still shows traces of its mode of develop- 

 ment, viz. by fusion of vacuolated cells, like the capillaries in 

 fig, 8. There are, however, other appearances which are in 

 perfect harmony with the vacuolation theory. Thus I have 

 before me a small patch with a network of capillaries, from 

 the wall of one of which solid protoplasmic threads of 

 great fineness extend, running in a slightly curved manner 

 over a distance of one to three millimetres, and ending in the 

 wall of a capillary vessel of a distant patch. The thread in 

 question contains seven spindle-shaped SAvellings, which 

 contain either a single nucleus or a small number of nuclei 

 (two, three, or four) ; in the latter case the fusiform swelling 

 shows more or less advanced vacuolation. There can be no 

 doubt that this thread will finally become converted into 

 a blood-vessel, for other such threads may be found in different 

 stages of development. Thus is explained the presence of 

 solitary capillary vessels found in the omentum, and extend- 

 ing from one vascular cell patch to another, sometimes for a 

 conspicuous distance — a distance occasionally to be measured 

 by the inch-measure. Besides the above nucleated proto- 

 plasmic vaso-formative threads there are other fine nucleated 

 protoplasmic threads, which appear to lose themselves in 

 the connective tissue of the matrix ; they are at some places 

 of great length (I — 3 mm.), and contain a nucleus at several 

 places at regular intervals ; they are probably nerves. I 

 believe I have seen them in connection, or what appears to 

 be a connection, with the vaso-formative threads. 



