OSMOTIC CONCENTRATION OF TISSUE FLUIDS 27 1 
the prevalence of fog, atmospheric humidity is high, ranging from 
about 80 to about 89 percent in the various months of the year, with 
an annual average of about 84 percent. 
Temperature is low and remarkably uniform throughout the year. 
At a depth of six feet at Cinchona the monthly mean soil temperature 
is 16.4° C, with a mean annual range of 1.5°. For air temperatures 
the annual mean is 16.0°, the annual mean range 2.9°, and the average 
daily range 6.6^. 
Our work was of necessity carried out within a radius sufficiently 
narrow to permit of the collections being made afoot, and brought 
back to the Laboratory for freezing within a few hours. Materials 
were drawn from the territory made accessible by the trail from 
Cinchona through Morce's Gap to a point somewhat south of Vinegar 
Hill, by that from Morce's Gap to John Crow Peak, by that from 
Cinchona to a point on one of the Green River affluents south of 
New Haven Gap, and by that from Cinchona through New Haven 
Gap to the lower slopes of Sir John Peter Grant Peak. Collections 
were by no means limited to the immediate vicinity of the trails, but 
were also drawn from the denser parts of the jungle, which was pretty 
thoroughly penetrated in various directions. 
While a few determinations are based upon collections made 
between 5,500 and 6,000 feet, especially from New Haven Gap and 
from the slopes and summit of John Crow Peak, the main bulk of our 
constants are based on samples gathered between 4,500 and 5,500 
feet. Below 4,500 feet conditions change rapidly. Thus at Resource, 
one mile south of Cinchona and 1,300 feet lower (3,700 as compared 
with 5,000 feet), the mean rainfall is about 68 as compared with 
about 106 inches per annum at the Laboratory. The fogs which are 
so characteristic a feature of the northern slopes of the mountains, 
and which roll over the ridges from the windward sides, are dissipated 
on the lower leeward (southern) slopes. Thus conditions are not 
merely warmer but far drier. Here, too, much of the natural vegeta- 
tion, which in most of the area studied was in a primaeval condition, 
has been replaced or distinctly modified by agricultural operations — 
chiefly the planting of Arabian coffee, which thrives and because of 
the superiority of the product is commercially profitable in a region 
so broken as to be useful for only the more valuable hand-tilled crops. 
Materials and Methods. — In order that the constants of the present 
study may be comparable with those derived from other regions it 
