SYMPATHETIC CELLS: NORWAY RAT 325 
animal, the first being found in my series at a body weight of 
120 grams. In this case the percentage of water in the brain 
was 78.69, which corresponds to the age of eighty-eight days— 
this happens to be exactly the age at which they first appeared 
in the Albino. The number of the pigmented cells tends to 
increase as the animal grows older. There are two cases among 
the older rats which show large numbers of pigmented cells, 
but most ganglia have only a few, even at the later ages. There 
is less increase in the number of these cells in the Norway, as 
contrasted with the Albino, than we should have expected. The 
pigment granules are black or greenish black in color. It was 
a matter of some surprise to find that in the gray pigmented 
rat the cells contained hardly more pigment than appeared in 
the Albino. 
Vacuolization of the cells 
Incidentally vacuoles have been noted in a very few of the 
cells in the superior cervical ganglion of the Norway, although 
none were observed in the Albino. Out of eighty cases only 
eight showed vacuoles in the cells and in an entire ganglion 
only one to three vacuolated cells have been found (table 6). 
Most of these cells have but one vacuole, which is oval in shape, 
and which may lhe close either to the nucleus or to the periph- 
ery, but in one cell two vacuoles were found. ‘The size of the 
vacuole varies; generally it is smaller than the nucleus, rarely 
larger. It resembles the nucleus in outline, but, owing to the 
absence of any internal structure, can be recognized without 
difficulty. All the vacuolated cells were found in older rats. 
Increase in the number of the large cells 
In counting the large cells found during the first twenty-five 
days, I followed the procedure previously used for the Albino. 
The cells of the Norway are small as compared with those of 
the Albino, especially at birth, so I have extended the limiting 
values, 19 to 25 », which were used for the diameters in counting 
the large cells of the Albino, to 16 to 25 » for the Norway. 
