544. U. S. BUREAU OF FISHERIES 
Observations on the pathology of chlorine poisoning indicate that 
extremely small quantities have the same general effect on fish that 
much greater amounts have on higher animals. Death is the result 
of suffocation induced by inhibition of the respiratory action. 
Whether this is due to constriction of the arterioles or to edema at 
this point is uncertain. The most striking symptom in gassed fish 
is the congestion of the visceral blood vessels. It is noteworthy that 
after exposure to chlorine for any length of time fish will not recover 
when removed to chlorine-free water. 
INVESTIGATIONS IN WISCONSIN LAKES 
During July and August, 1926, limnological studies were con- 
tinued on the lakes of northeastern Wisconsin by the Geological 
and Natural History Survey of that State in cooperation with the 
Bureau of Fisheries. Observations were made on 73 lakes, most of 
them situated in Vilas County. Forty-six of these were visited in 
1925, but 27 were visited for the first time in 1926. 
Biological and chemical laboratories were established in two build- 
ings at the State forestry headquarters at Trout Lake, Wis. Two 
biologists, Dr. E. A. Birge and Prof. C. Juday, and two chemists, 
Loren C. Hurd and Rex J. Robinson, were engaged in this investi- 
gation. 
Tn size, the various bod:es of water ranged from a minimum of an 
acre or two to a maximum of 1,500 acres. The depths varied from 2 
meters to 35 meters: in most of them the maximum depth does not 
exceed 15 meters. 
The lowest surface temperature noted was 18° C., and the highest 
was 23.5°. The temperature of the bottom water in the deeper lakes 
varied from 4.7° C. to 10°, but the temperature of the bottom water 
in the shallow lakes was substantially the same as that of the surface. 
A complete set of chemical and biological determinations on a 
sample of water comprised 14 different items, not including a read- 
ing of the temperature of the water at the time the sample was 
taken. A single series of samples, extending from surface to bottom, 
in Trout Lake, for example, included 83 different determinations 
in addition to 14 temperature readings taken at the time the samples 
were obtained. Field methods have been developed that make it 
possible to complete such a set of determinations in one day. 
These lakes have relatively soft water; the fixed carbon dioxide 
ranges from a minimum of less than 1 cubic centimeter per liter 
of water to a maximum of a little more than 15 cubic centimeters. 
In 25 of these bodies of water the fixed carbon dioxide was less 
than 2 cubic centimeters per liter of water, but most of the others 
had between 5 and 10 cubic centimeters. The bottom water of some 
of these lakes possessed a distinctly larger amount of fixed carbon 
dioxide than the surface water; in Wild Cat Lake, for example, the 
surface water possessed 15.4 cubic centimeters per liter and the bot- 
tom water (11 meters) 22.3 cubic centimeters on August 24, 1926. 
The lowest readings for hydrogen-ion concentration were obtained 
in the lakes having the softest water; that is, in those having less 
than 2 cubic centimeters of fixed carbon dioxide per liter of water. 
In such lakes the reaction varied from pH 5.2 to pH 6.5. In the 
lakes having a larger amount of fixed carbon dioxide the range was 
