PHYSIOLOGICAL STUDIES OF THE CHINOOK SALMON. 447 



of — 0.762 : C, i. e., the total depression due to all the blood constituents and equiva- 

 lent to 1.26 per cent" of sodium salt (see ante). The percentage of sodium chloride 

 present in sea water, according to an analysis of the North Sea water by Harks, 6 is 

 2. 358 per cent in a total of 3.046 per cent of salts. Applying this analysis to the sea 

 water of Monterey, where the salmon are taken, it is obvious that there is a difference 

 in concentration between the sea water and the salmon blood in sodium chloride 

 alone of a little less than 2 per cent, a difference which ought to suffice on known 

 laws of osmosis in establishing a strong current of water from the blood to the sea 

 water. 



Furthermore, the salmon are feeding constantly and voraciously at this time, a 

 process which may introduce considerable sea water into the stomach. This is notably 

 true at Monterey, where the chief food is the squid, the blood and body fluids of which 

 have the concentration of sea water.* The skin, also, is a possible region of exchange 

 of constituents between the blood and the sea water. Neither of these regions 

 provides a channel by which the salts of the sea water may permanently enter the 

 blood. 



Enough has been given here to demonstrate that we do not have to deal with a 

 question of simple osmotic balance between the sea water and the salmon's blood. 

 Such a balance does not exist. The living epithelium of the gills does not act like 

 an ordinary dead animal membrane; it is, in fact, a membrane impermeable, or at 

 most permeable with great difficulty, to both water and salts. This question will be 

 reviewed after presentation of the facts concerning the relations of the blood in 

 fresh-water salmon from the upper streams. 



THE BLOOD OK SALMON FROM TIDE WATER. 



The blood was collected from seven different specimens of salmon taken near 

 Black Diamond, California, in August, 1902, all from the main channel off' Collinsville. 

 The water in this region at the time of my examination lowered the freezing point 

 by only —0.020° to —0.022° ('., an amount that is insignificant as compared with 

 the depression of the freezing point of sea water. 



'i The percentage obtained by interpolation from Hedin's tables (Skand. Arch.,Bd. 5, 1895, s. 381 1 is somewhat less, i.e., 

 1.22 percent. 



bQnoted from Griffith's Physiology <>i Invertebrate, p. 137, New York. 1892. 



cBottazzi, La pression osmotique du sang des animaux marins. Archives iteliennes de Biologie, I '. 28, 1897. p. 61. 



