2936. Thus the secernent organ of the general circulation must belong to the sexual system, and perform in it that which the liver, or in other words the reverse of the lungs, has done in the splanchnic circulation. The kidneys are the lungs reversed.
2937. If the bile be an extract from the visceral blood, so is the urine an extract from the body's blood, and is consequently the purest reflex or pattern of the former.
2938. The urine is sexual blood, just as the excrement is a product of the sexual digestion. The urine is reversed blood.
2939. The formation of urine is a retro-formation of the blood into digestive fluid or sap. The urine is blood of the sexual animal which has become chyle. It has both properties in itself. It is discoloured blood, and consists for the greatest part of water and salts, all of which are characters belonging unto chyle. It, however, contains urea, which corresponds to the noblest parts of the blood. This substance, like fibrine, consists for the greatest part of nitrogen; it may be called dissolved or decomposed fibrine. It imparts colour to the urine; it is converted by oxydation into lithic or uric acid, and is precipitated of a red colour analogous to that of the blood-globules. In addition to this, albumen, gelatine, carbonate of lime, and phosphorus, consequently the whole blood, are present in the urine.
2940. In urea the muscle flows or runs out of the animal, in albumen the nerve, in lime and phosphorus the bone, in gelatine the tegumentary together with the visceral system, lastly, in water the menstruum of the digestion and respiration.
2941. Thus the urine, just like the blood, is the whole body rendered fluid, but only in a sexual manner, namely, as being half decomposed.
2942. So the bile, from its not representing the whole body, does not contain the latter in itself. It properly contains only the excretion of the intestinal process.
2943. The kidneys stand accordingly opposed without distinction to all the organs, in so far as all of them are affected by the circulation. Their remote sympathy, or if we please, their antagonism, is with the animal systems, or with bone, muscle, and nerve. With the osseous, as being the profoundest system, there is of necessity also a close sympathy. In diseases of bone the bones, as well as the morbid matter, flow away principally through the urine. Their most intimate sympathy must be with the organs of circulation, with the lung, liver, intestine, and skin. As the skin is also an organ of evaporation, so is the antagonism between it and the kidneys of a direct or immediate kind. The skin is the kidneys expanded into a large cyst. These are in turn, just as the lung is, the inverted skin.
2944. A lung in the reversed animal can do nothing else but expire. It only expels the evaporated matter of the sanguinary system, but takes in none, so as to alter or support the blood. The sexual animal aims at the destruction of the animal. The urinary cyst, as being the remnant of the allantois, and of the primordial kidneys or sexual branchiæ, is simply destined to purposes of expulsion. It is the larynx reversed. Micturition takes place through contraction of the cyst, as does expiration by that of the lungs in Reptilia. It is a cough.
B. FUNCTIONS OF THE ANIMAL SEXUAL ORGANS.