VOIi. LIX.] PHILOSOPHICAL TRANSACTIONS. 66g 



the presence of many witnesses; so that, without using the knife or lancet, the 

 least force or violence, air may be thrown into the lymphatics from their very 

 beginnings ; and mercury may be made to pass by the same orifices. 



Though I have said we may easily have an ocular demonstration of the origin 

 or mouth of the lymphatic, in this part of the human body, I must confess it 

 is not always we can have that satisfaction : no part is more frequently diseased : 

 inflammation solders up the mouths of these little vessels; and it is not to be 

 expected we can show their orifices when the urethra is in such a state. It will 

 always require some dexterity to catch the opening of the lymphatic; but the 

 bristle, once fairly introduced, will generally pass with great ease some way 

 within the vessel. Here then we may satisfy ourselves in what manner the 

 lymphatics do actually begin from surfaces: and to those who, without ever 

 having seen the origin of a lymphatic, have nevertheless reasoned so well, and so 

 justly, on this subject, it may perhaps afford some pleasure and satisfaction to 

 find their conjectures agreeing so perfectly with the structure. 



The situation of the lymphatics, in general, is superficial; that is to say, they 

 are mostly to be seen on surfaces; though there are some deeper seated ones, 

 which accompany the blood-vessels. They have been well described by authors, 

 as exceedingly fine, tender, and transparent vessels, frequently joining into one 

 another, and intersected by a number of very delicate membranous pouches or 

 valves; so that, having an injection thrown into them, they give the appearance 

 of being full of little knots. The lymphatics are apparent enough, when they 

 unite and grow large ; but from their exility, want of colour, and transparency, 

 they are very difficult to be discovered before. 



Owing to these circumstances it is, that their origins have never before been 

 seen ; and that in many parts of the body, where they are nevertheless supposed 

 to exist, they still lie unnoticel. Haller, after speaking of these vessels in many 

 other parts of the body, goes on thus : • Quae a pene veniunt mihi minus nota 

 sunt, sed dicta Cowpero. Alia hue a vesiculis seminalibus tendunt, aut certe ab 

 earum vicinia, aut a vesicae urinariae sede, aut ab ipsa demum vesica, quae quidem 

 vascula iterum fateor mihi nondum visa esse.' So that Haller, who knows so 

 well the structure of the human body, knows nothing of these lymphatics of the 

 bladder, or membranous portion of the urethra. The lymphatics of the urinary 

 human bladder and urethra, first appear on each side the verumontanum or ca- 

 put gallinaginis, and by very little orifices take their origin from the internal 

 membrane that lines the urethra and bladder, on whose surface they open. In 

 their natural state, they appear like so many fine threads lying close together, 

 but diverging afterwards, as they pass over the prostate gland and neck of the 

 bladder, and inosculating or communicating very frequently, they form a kind of 

 network or embroidery. Hence they are continued through the cellular mem- 



