688 THE POPULAR SCIENCE MONTHLY. 



cessantly at work, have a highly-developed arterial system. The 

 blood is renewed in the glands as in all the tissues, and the dilatable 

 walls of the vessels admit it in different proportions, according to the 

 state of rest or activity of the organ. In this case, as in all others, 

 particular facts are merely the expression of a more general law. The 

 flow of blood increases when a stimulant exerts its action. When a 

 glandular element acts with energy, it produces a high degree of ful- 

 ness of blood in all the neighboring parts ; and physiologists have 

 thoroughly proved this fact in the case of the salivary glands of ani- 

 mals. In a state of rest, the congestion of these glands is slight, the 

 blood dark in the veins issuing from them ; the organ is then gaining 

 growth. When the animal taken for experiment emits saliva under 

 the influence of artificial stimulus, the glands, on the contrary, fill with 

 blood, the vessels grow turgid, and take a high vermilion color. Thus 

 variations in the supply of blood always coi-respond with degrees in 

 secreting activity, and secretion ceases when the blood no longer 

 comes to the glands. If the vessels of the liver are obliterated, bile ' 

 ceases to be formed ; if the arteries of the kidneys are compressed, 

 secretion by those organs stops. The statement of the conditions of 

 the problem suffices to suggest its solution ; the blood is a medium 

 whence the glands draw the principles of their growth and functions ; 

 the circulation of the sanguine fluid within the glandular tissue is a 

 true transfusion kept up incessantly by the heart, and which only arti- 

 ficial transfusion can be a substitute for. 



Nutrition and secretion by their constant work keep up the organ- 

 ized state of vegetable and animal matter. Plants possess only these 

 two functions, and we may almost say the same thing as to animals 

 while asleep; but these are not the only functions assigned to the 

 waking animal, which comes into relations with the external world, 

 through motion, sensibility, and intelligence. The muscular fibre, the 

 special organ of motion, has its activity, independent of the nervous 

 system ; local transfusion confirms this scientific view, which now 

 rests on manifold proofs. Like the secreting element, the muscular 

 fibre is distinct in some lower animals ; the microscope detects it in 

 that state in the transparent body of the infusoria called vorticelli. In 

 the his/her decrees of the animal series this fibre is found in connection 

 with nerves and vessels, and, , though it enjoys an excitability peculiar 

 to itself, it receives an impulse to movement from the motor nerve. 

 The contact of the muscular fibre with blood-vessels is very close ; but 

 the chemical composition of the blood that moistens it varies ac- 

 cording to the quantity of work yielded ; thus it is indispensable that 

 new fluid should be constantly transfused into the net-work of veins 

 in the muscle. If the motor fibre is at rest, the blood passing through 

 it is scarcely modified. If it is in a state of half contraction, the 

 oxygen decreases in the blood, and the carbonic acid increases. If 

 contraction is evident and powerful, combustion and production of car- 



