ZOOLOGY. 375 



latter having been imprisoned artificially, while the former had become a per- 

 manent resident in fresh water from natural causes alone. 



At a subsequent meeting, Professor Agassiz, in reply to a question 

 whether the fishes of the European coast could be transplanted to the 

 shores of America, said that it was extremely doubtful. From a general 

 point of view he should not suppose that any family of fishes, which have 

 no representatives here, could flourish on this coast; but that perhaps fish 

 belonging to the same family with the haddock and hake, might be nat- 

 uralized. 



VARIATION OF COLOR IN THE VENOUS BLOOD OF THE GLANDS. 



Since the discovery of the circulation of the blood, it has been admitted 

 that the blood of the arteries is red, and that of the veins black, with this 

 exception, that it is the reverse for the arteries and pulmonary veins. This 

 fact has afforded Bichat the foundation for his grand division of the circula- 

 tion (since adopted by all anatomists), a vascular system with red blood, 

 which carries the blood from the lungs to all parts of the body ; a vascular 

 system of black blood, which carries the blood from all parts of the body to 

 the lungs. But it results from the researches of Prof. Claude Bernard that 

 this statement cannot be accepted absolutely. This skilful observer has 

 proved, through a great number of dissections of living subjects, and in a 

 manner which leaves no room for doubt, that the blood contained in the 

 renal veins is sometimes black and sometimes red, and that when it has 

 the latter color, it is black in the inferior vena cava which receives the blood 

 from the renal vein. 



This fact being established, he looked for an explanation, and found that 

 it was due to the state of repose or activity of the kidneys, the secretory 

 organ of the urine. He has, in fact, demonstrated, by delicate experiments, 

 in his course of Physiology at the College of France, that when the urine 

 runs from the kidneys, where it has just been formed, in the ureter which 

 takes it to the bladder, the blood contained in the renal cavities is red ; and 

 that it becomes black when the flow ceases. 



The same experiment performed on the submaxillary gland of the dog 

 produced the same result. Flowing of saliva by the proper duct from this 

 gland, and presence of red blood in the afferent vein are two phenomena 

 which go together, as also the absence of saliva and black color of the blood 

 in the same vein. Analogous experiments made on the parotid gland and 

 on the glands in the abdominal parts of the digestive tube, have given sim- 

 ilar results. But the author adds, with the habitual severity which he brings 

 to his conclusions, that the study will be complete only when the examina- 

 tion shall have been extended to every gland throughout the structure. 



It results from the facts, that if, as regards physiological conditions, the 

 term red blood may be applied to the arterial blood, that of black blood can- 

 not be used in so general a way for the venous blood. It results also, from 

 other researches of Prof. Bernard, that physical and chemical modifications 

 correspond to these different states of coloration, and ought to be taken into 

 consideration in the analyses of the blood, the composition of which varies 

 even with the state of activity or repose of an organ. The last principle 

 applies not merely to the glands, but to all the organs of the body; so that 

 it will be necessary to study now the venous blood in the state of repose, 

 and in the state of functional activity. It is worthy of remark, that if the 



