I3SO 



VEIN. 



margin of the valve. The fibres are singularly 

 regular, and present the most beautiful and 

 equal undulations, as if eacli fibre were of 

 exactly the same size and extent ; and the un- 

 dulations of all succeeding fibres are precisely 

 similar, as far as the tenuity of the structure 

 towards its attached margin is sufficient to 

 allow of its examination. These fibres may 

 be looked upon as a portion of the circular 

 coat protruded into the cavity of the vein. 



Fig 8G5. 



Small Portions of the Valves from a Sheep. 



A, The valve showing a line of epithelial nuclei at 

 the extreme margin a a' ; a', detached nuclei ; b, 

 small portion of face of valve, exhibiting wavy 

 fibres, epithelium and muscle. 



B, the same treated with acetic acid, a a, margin. 

 On the face of this valve are seen two sets of 

 nuclei ; and fine threads of elastic fibre. (Mag- 

 nified 200 diameters.) 



Running at right angles to these, and placed 

 upon a different plane, are to be seen fibres 

 or elongated corpuscles of a spindle shape, 

 and of very variable distinctness. These cor- 

 puscles are apparently muscular fibre-cells: 

 they are very conspicuous in some specimens, 

 and very indistinct in others ; whilst in others 

 they cannot be discovered at all. 



On treating a valve with acetic acid, two 

 sets of nuclear corpuscles are to be discovered, 

 running at right angles to each other. Those 

 which are parallel with the wavy fibres of the 

 fibrous lamina are mainly oval, interspersed 

 with a few more elongated ; and those, cutting 

 the former at right angles, and being parallel 

 with the muscular fibre-cells, are club-shaped 

 and spindle-shaped, having a strong resem- 

 blance to the nuclei of muscular fibre-cells. 

 The former, as it appears to me, are mainly 

 persistent nuclei of areolar tissue, and belong 

 to the wavy fibres, whilst the latter are evi 

 dently muscular nuclei. Small threads of yel- 

 low fibre are occasionally seen. They are 

 very fine, detached and scattered ; and fre- 

 quently exhibit a spiral form. In examining 

 these structures it is necessary that, when 

 removed from the body, they should not be 

 allowed to dry before the observations are 



completed ; for the characters both of the 

 fibrous lamina and nuclei are impaired per- 

 manently if they have once been dry. 



Sinuses. There is yet another item in the 

 valvular apparatus of venous canals, the oc- 

 currence of sinuses in the walls of the veins. 

 These consist of small pouches or dilatations 

 in the walls of the veins immediately in front 

 of the valves. By these, the cylindrical form 

 of the vessel is lost at that spot, two bulgings 

 being apparent on it. These bulgings pro- 

 duce a certain amount of attenuation at 

 these points, the thinness being in direct 

 proportion to the increased area produced. 

 The sinuses vary in dimensions, and do not 

 bear any exact proportion to the size of the 

 valve. Lateral dilatations maybe seen in the 

 walls of veins where no valves are present. 

 (Seej%.,863., b',g, e , h.} When the valves are 

 in action, these distended sinuses present knots 

 along the course of the vessel ; an appear- 

 ance first described and figured by Fabricius : 

 he observes of them, " non dissimilem for- 

 mam exterius pras se fl rentes, ac nodi in plan- 

 tannn raniulis, et caule apparent."* 



The supply of valves in the venous system 

 is only partial, and is irregular. Valves 

 are only found (in the human subject) in 

 those veins which are subjected to muscular 

 pressure, and are, therefore, most abundant in 

 the veins of the limbs : and it has been well 

 laid down by Cruveilhier, " that their pre- 

 sence and their number, their proximity and 

 their distance from each other are directly 

 influenced by the degree of opposition to the 

 onward progress of the blood in any set of 

 veins." -J- 



Of the veins of the head and neck, the ex- 

 ternal jugular is the only one with valves: it 

 possesses two, which however are not suffi- 

 ciently compact to oppose injection. There 

 are none in the cerebral sinuses or veins, and 

 none in the internal jugular. The veins of 

 the upper extremity are abundantly supplied 

 with valves, which appear to be somewhat 

 more numerous near the upper part of the 

 arm. There are valves in the axillary vein, 

 but none in the subclavian, vena innominata, 

 or superior cava. They are abundant in the 

 lower extremity, but most numerous at its 

 lower part ; in this respect differing from 

 the superior extremity. The branches of the 

 internal iliac vein are supplied with valves, 

 while the external and internal iliacs them- 

 selves, the common iliac, and the inferior cava, 

 have none. The spermatic veins (male) have 

 valves, while the ovarian (female) are desti- 

 tute of them. In the azygos veins, Cruveil- 

 hier denies the existence of valves, but they 

 are occasionally found in an imperfect state 

 of development. 



The spinal veins are destitute of valves, as 

 are, also, those of the portal system, the he- 

 patic veins, those of the heart, kidney, uterus 



* Loc. cit. For figures of these " nodi," see Fa- 

 bricius, Opera omnia, tab. II. p. 157. ; also Harvey, 

 De Motu Cordis et Sanguinis in Animalibus, Ana- 

 tomica Exercitatio. Lugd. Bat. 1639, p. 187. 



f Cruveilhier. Anatomic Descriptive. 



