PERFUSION 



189 



PERMEABILITY 



an outlet near the bottom or a bent glass 

 tube siphon connected by a rubber tube 

 about 6 feet long with a glass Cannula. 

 An arterj' clamp placed about 1 foot from 

 the cannula will serve as a shut off. 



If one wishes to perfuse a mouse the 

 best way is to tie a small cannula into 

 the ventricle, if it is the abdominal 

 organs of a guinea pig the following pro- 

 cedure is advised : Kill the animal with 

 chloroform if this anesthetic will not 

 interfere with the results as is seldom 

 the case. Cut carotids and jugular 

 veins to partly exsanguinate the animal. 

 Clip away sternum and most of the ribs. 

 Displace left lung, expose thoracic aorta 

 and free a portion of it from surrounding 

 tissue. Pass moistened ligature thread 

 behind aorta. Make with scissors a 

 small slit in wall of aorta not at right 

 angles to it but directed into it and 

 downward (toward tail) being careful 

 not to cut more than | through it. In- 

 sert wet cannula into the slit with slight 

 rotatory motion until the constriction 

 in the cannula is about 1 cm. within the 

 aorta. Then bring the two ends of the 

 thread together and tie the cannula in 

 place. Remove clamp from rubber tube 

 and allow fluid to flow in from bottle 

 suspended about 4 feet above cannula, 

 open right auricle to permit free exit of 

 fluid. It may be necessary to clamp in- 

 ferior vena cava just above diaphragm 

 and increase pressure somewhat. Some- 

 times it is helpful to vary pressure by 

 opening and closing clamp. After 4 or 

 5 minutes open abdomen and examine 

 organ which it is desired to perfuse. 

 The absence of blood color in it and the 

 color of the perfusate (if colored) are 

 indicators of completeness of the oper- 

 ation. The pancreas and the liver will 

 swell considerably but this may not be a 

 disadvantage. 



Pericapillary Cells, or pericytes, are closely 

 applied to, or wrapped about, the endo- 

 thelium of blood capillaries. The desig- 

 nation relates to position only and it 

 includes cells of several sorts from 

 much branched Rouget cells to simple 

 fusiform muscle cells and connective 

 tissue cells. Methods of silver im- 

 pregnation and beautiful illustrations 

 are provided by Zimmermann, K. W., 

 Zeit. f. Anat., 1923, 68, 29-109. The 

 myofibrils in contractile pericapillary 

 cells can be stained supravitally with 

 janus green, (Bensley, R. R. and Vim- 

 trup, R., Anat. Rec, 1928, 39, 37-55). 

 Valuable data can be obtained by micro- 

 dissection of the living tissues (Zwei- 

 fach, B. W., Am. J. Anat., 1937, 60, 

 473-657). 



Pericardium. Special dissections of bands 

 of fibers in pericardium (Popa, J. T. 

 and Lucinescu, E., J. Anat., 67, 78-107) . 



Methods for study of absorption of sub- 

 stances placed in pericardial sac (Drin- 

 ker, C. K. and Field, M. E., J. Exper. 

 Med., 1931,53, 143-150). 



Peritoneal Fluid. Cells present (Webb, 

 R. L., Am. J. Anat., 1931-32, 49, 283- 

 334; Folia Haemat., 1933, 51, 445-451). 



Periodontium, see method for Teeth and 

 Jaws. 



Peritoneum. Outlines of mesothelial cells 

 blackened with silver nitrate (Pumala, 

 R. H., Anat. Rec, 1937, 68, 327-338, 

 good illustrations). Exudate cells 



stained vitally with lithium carmine 

 (Maximow, A. A., Cowdry's Special 

 Cytology). 



Perivascular Spaces of the brain. The Weed 

 McKibben method (Weed, L. H., Am. 

 J. Anat., 1923, 31, 191-221), based on 

 dehydrating the brain by increasing 

 osmotic pressure of the blood and draw- 

 ing into these perivascular spaces solu- 

 tions of potassium ferrocyanide and 

 iron ammonium citrate, after injection 

 into the subarachnoid space, and their 

 later precipitation as Prussian blue by 

 fixing tissue in acid formalin, has been 

 modified by Patek, P. E., Anat. Rec, 

 1944, 88, 1-24. In rabbits and cats he 

 injects intravenously 6-S cc. 30% aq. 

 sodium chloride during 10 min. and 

 3-4 cc particulate suspension of India 

 ink or mercury sulfide in the cisterna 

 magna under atmospheric pressure dur- 

 ing 15-20 min. The animal is then 

 killed by bleeding and perfused via 

 the aorta with 10% formalin. After 

 further fixation of brain by immersion 

 1 mm. slices are cut and mounted un- 

 stained or the tissue maybe imbedded 

 in paraffin in celloidin and 10-50 n sec- 

 tions colored with gallocyanin or some 

 other appropriate stain. Dogs can also 

 be used as he directs. 



Permeability. This is a fundamental prop- 

 erty for the study of which there are 

 many microscopic techniques. The 

 idea that what goes in and what comes 

 out through the plasma membrane (see 

 Cell Membranes) always depends upon 

 the character of the particular substance 

 and of the membrane is fallacious. By 

 his method of observing in vivo the ruffle 

 Pseudopodia of macropliages and can- 

 cer cells W. H. Lewis (Am. J. Cancer, 

 1937, 29, 666-679) has enabled us to see 

 tliat materials can be drawn into the cy- 

 toplasm in invaginations of the plasma 

 membrane which lose connection with 

 the outside so that when the isolated 

 membranous investments disintegrate 

 the materials are liberated in the cyto- 

 plasm without ever traversing the intact 

 surface plasma membrane. This is the 

 converse of observations made possible 

 by the direct examination of secreting 

 acinous cells of the pancreas by W. P. 



