This section is from the book "The Sushruta Samhita", by Kaviraj Kunja Lal Bhishagratna. Also available from Amazon: The Sushruta Samhita.
In the present work, as well as in other works of recognised authority, a month is calculated to consist of eighteen thousand and ninety Kalas.
The said Rasa courses through the whole body in invisible currents of zigzag shape, like the waves of sound, or in (an upward direction) like flames of fire, or (in a downward direction) like rivulets of water.
Now it may be asked, since the Rasa is naturally transformed into semen in the course of a month, what is the use of administering medicine which has a stimulating effect upon the organs of generation (Vajikaranam.) The answer is, that such medicines out of their own specific potencies and virtue help the speedy conversion of Rasa into semen and its profuse emission [on the desired occasion] like purgatives aiding the drastic evacuation of the bowels.
Again it may be asked, how is it, that semen is not found in an infant? Since perfume in a flower-bud is imperceptible to the organ of smell you may as well ask whether there is any perfume in it or not. But what does not exist in a thing can not be evoked in the subsequent course of its development. As the perfume in a flower-bud lies latent in its early stage of growth but becomes patent only with the growth of its seed organs, so semen or catamenial blood lies in a potential state in a male or a female child, and appears with the growth of beards and mustaches, or with the enlargement of the breasts, uterus and vaginal canal and the appearance of pubic hair.
The same Rasa, originated from the assimilated food, serves only to maintain the vitality in the old and spontaneously decayed subjects owing to an exhausted state of the inner vitalising principle, natural to old age.
The abovesaid principles (of Rasa, blood etc.) are called the root principles (Dhatus), inasmuch as they maintain the integrity of the human organism and guard against its speedy dissolution). And since the strength or weakness of the abovesaid bodily principles absolutely depends upon the richness or poverty of blood, we shall discourse on the latter condition of the blood.
The blood, vitiated by the deranged bodily wind (Vayu), becomes thin, frothy, transparent, quick- coursing, and expansive, assumes a vermilion or black hue, and is divested of its slimy character; whereas vitiated through a deranged condition of the bile (Pittam), it assumes a blue, yellow, green, or brown colour, emits a fishy smell, becomes thin in its consistency and is shun by flies and ants. Similarly, blood, vitiated by the deranged phlegm (Kapham), becomes cold, glossy and thick, assumes a colour like that of the washings of Gairika or that of a flesh tendon, takes time in secreting or in miming down, and is marked by an increase of its slimy character. The blood, vitiated through a concerted derangement of the three bodily humours, is marked by features peculiar to each of them, and assumes a colour like that of Kanjika (sour gruel), and emits a fetid smell. Similarly, the blood, vitiated through the joint action of any two of the (beforesaid) bodily humours, is characterised by features peculiar to each of them.
The blood in its healthy and natural state is possessed of a vivid red colour like that of an Indragopa (Cochineal) insect, and is neither too thin nor too transparent. *
 
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