ARTERIOLES 



22 



ARTIFACTS 



the intramural vessels their arrangement 

 can be studied (see Vasa Vasorum). 

 Fatty substances can also be located 

 because they are not removed by the 

 glycerin. 



Chief reliance is ordinarily placed in 

 the appearance of arterial walls when 

 seen in sections of fixed tissue. It is 

 important to remember that, when carry- 

 ing blood during life, the lumina are 

 larger and the walls less folded than in 

 the fixed condition. The difference has 

 been graphically demonstrated by Gallo- 

 way, R. J. M., Am. J. Path., 1936, 12, 

 333-336. His figures should be exam- 

 ined. For routine purposes fixation in 

 Formalin-Zenker followed by Mallory's 

 Connective Tissue Stain supplemented 

 by Resorcin Fuchsin or Orcein for 

 elastic tissue is satisfactory. Special 

 methods may be needed for Lipids ; and 

 for minerals, see Calcium, Iron and 

 Microincineration. Innervation, like- 

 wise, is to be studied by methods em- 

 ployed to demonstrate Nerve Endings 

 in other tissues. See Vasa Vasorum. 

 Much literature on techniques is given 

 by various authors in Cowdry, E. V., 

 Arteriosclerosis, New York: Macmillan, 

 1933, 617 pp. The investigation of 

 arterial walls is apt to be one sided 

 limited only to structure and composi- 

 tion demonstrated microscopically. It 

 is high time that these lines of study 

 are supplemented by accurate meas- 

 urement of the physical properties of 

 pulse wave velocity, sound production, 

 elasticity and so on of the same vessels 

 by methods described by Bramwell in 

 the above mentioned volume. 

 Arterioles, capillaries and venules, in con- 

 trast to the much larger arteries and 

 veins, can readily be examined in experi- 

 mental animals microscopically in the 

 living state. Since they are linked 

 together a single preparation by Sandi- 

 son's rabbit ear method shows all three, 

 or they may be viewed in the living 

 tadpole's tail or other transparent tissue 

 of lower forms. For convenience, how- 

 ever, it seems best to briefly mention 

 the microscopic techniques for each 

 separately. There is much to choose 

 from. Information is frequently de- 

 manded on the condition of the arterio- 

 lar walls. This can best be supplied 

 by staining paraffin sections of Forma- 

 lin-Zenker fixed material with Mal- 

 lory's Connective Tissue stain or with 

 Masson's Trichrome stain which is 

 closely related to it. Weigert's Re- 

 sorcin Fuchsin is satisfactory for elastic 

 tissue. The Silver Citrate technique is 

 capable of yielding valuable data on arte- 

 rioles and capillaries. Because arte- 

 rioles contain a higher percentage of 



muscle than any other blood vessel their 

 appearance will vary greatly with the 

 degree of contraction or relaxation of 

 muscle. According to Kernohan, J. W., 

 Anderson, E. W. and Keith, N. M., 

 Arch. Int. Med., 1929, 44, 395-423 in 

 fixed preparations from normal persons 

 the average ratio of thi ckness of arteriolar 

 wall to width of lumen is 1:2. 



Arteriovenous Anastomoses are direct con- 

 nections between arteries and veins 

 vrithout intervening capillaries. No 

 special histological technique is required 

 for their demonstration in sections but 

 one should look for them where they are 

 particularly numerous, as in rabbits at 

 the tip of the nose (diameter, 80-100/i) 

 and in humans in the palms of the hands, 

 the soles of the feet and near the ends 

 of the fingers where their diameter is 

 about 35m (Grant, R. T. and Bland, 

 E. F., Heart, 1930, 15, 385-411). The 

 best way is to study them in vivo (Clark, 

 E. R. and E. L., Am. J. Anat., 1934, 55, 

 407-467). 



Arteriosclerosis. The arteries in this condi- 

 tion show changes well demonstrated 

 by Mallory's Connective Stain and its 

 modifications as well as by Weigert's 

 Resorcin Fuchsin. In addition, tech- 

 niques for Lipids, Calcium and Iron are 

 indicated. Methods for the measure- 

 ment of physical properties of arteries 

 might well be applied to arteries most 

 and least prone to develop arterio- 

 sclerosis. These are summarized by 

 Bramwell, C, in Cowdry's Arterio- 

 sclerosis. New York: Macmillan Co., 

 1933, 617 pp. 



Artifacts. Webster defines an artifact as 

 being "in histology, a structure or 

 appearance in a tissue or cell due to 

 death or to the use of reagents and not 

 present during life." The degree of 

 artifact is proportional to the difference 

 between the structure existing normally 

 in the living body and the structure in 

 the condition directly studied. 



1. In the case of living tissues, ob- 

 served with blood and nerve supply 

 intact, there is a possibility of artifact. 

 It is at a minimum in the Rabbit Ear 

 Chambers and rather more to be reck- 

 oned with when tissues must be dis- 

 placed in order to supply the necessary 

 illumination. With increase in time 

 modifications due to changes in light, 

 temperature, hydrogen ion concentra- 

 tion, etc. are likely to also increase. 



2. In living cells removed from the 

 body and examined in Tissue Cultures 

 the possibility of artifact is again at a 

 minimum ; but, though the cells in suc- 

 cessive generations in suitable media go 

 on living indefinitely, their environ- 

 ments are different from those existing 



