SILVER'S 



225 



SKIN 



hrs. Remove and examine. When com- 

 plete, generally before a grossly visible 

 reduction of silver is evident in the 

 solution, remove, wash in 2 changes aq. 

 dest., dehydrate, clear and mount. 

 More finely myelinated fibers are re- 

 vealed than are demonstrated by the 

 standard Weigert technique. 



2. For myelin sheaths and mito- 

 chondria fix with 10% formalin in 1% 

 aq. potassium bichromate or with 10% 

 formalin in 1% aq. NaCl again prefer- 

 ably by perfusion, and mordant small 

 blocks of the tissue in 3% aq. potassium 

 bichromate for 7 days (This mordanting 

 can be dispensed with if tissue is in 

 fixative for more than 1 week.). Wash, 

 dehydrate, imbed (in paraffin), cut 

 4-20m and mount on slide. Remove 

 imbedding medium and proceed as 

 described above. 



Sinusoids are capillaries of large diameter 

 through which the circulation is slower. 

 The endothelial cells of their walls 

 ingest some forms of particulate matter 

 in the blood stream. The best place to 

 demonstrate them is in carmine stained 

 sections of formalin fixed liver of an 

 animal injected intravenously with 

 India ink as described under Vital 

 Staining. 



Sizes of Organs. See Normals. 



Skin. No other part of the body is simi- 

 larly spread out for examination in vivo. 

 Much is to be gained by correlation of 

 gross and microscopic study. Altera- 

 tions in color, moisture, consistency and 

 thickness can easily be detected. 

 Changes in sensitivity and in the num- 

 ber and activity of sweat glands can be 

 determined by appropriate methods. 

 Simple techniques are available for the 

 visualization of Lymphatic Vessels, 

 and the Capillaries in the dermal papil- 

 lae can be demonstrated microscopically 

 and their behavior recorded in moving 

 pictures. See Thomas Lewis' classic, 

 The Vessels of the Human Skin and 

 their Responses. London : Shaw & 

 Sons, 1927, 322 pp. Very important is 

 direct study of the skin with hand 

 lens or binocular microscope. 



But examination in sections will 

 always remain the basic method of 

 study. Hair, where present, should be 

 cut short with scissors and removed 

 with an electric razor, an instrument 

 which does not require the use of any 

 soap and does not scrape away the sur- 

 face. Samples of skin removed at 

 autopsy are satisfactory for some pur- 

 poses up to about 24 hrs. if the body has 

 been kept cool because autolytic changes 

 take place comparatively slowly in the 

 skin. But biopsy specimens are much 

 better. The local anesthetic should be 

 injected in a circle about the skin to be 



excised and the observer should be on 

 the lookout for slight modifications if the 

 sections include the actual area into 

 which it is forced. Obviously the 

 specimen should be lifted, never 

 pinched with forceps. 



Because the skin is made up of 2 tis- 

 sues, avascular epidermis ana vascular 

 dermis, closely bound together, differ- 

 ential shrinkage is a troublesome factor. 

 Evans, R., Cowdry, E. V. and Nielson, 

 P. E., have found in this laboratory 

 that, owing to shrinkage or drawing to- 

 gether of the dermis, the folds in the 

 epidermis are accentuated to an extent 

 much greater than is generally realized. 

 This is more marked in young skins than 

 in those of old people and in living skin 

 than in skin excised after long delayed 

 autopsy. It is apparently not feasible 

 to entirely side step this kind of artefact 

 but the tendency of the whole specimen 

 to curl up can be obviated by spreading 

 it out with dermis down on a piece of 

 wooden tongue depressor or stiff card- 

 board for the first few minutes of fixa- 

 tion. If interest definitely centers in 

 the dermis it should be mounted with 

 epidermis down. But it should not be 

 kept in either position too long because 

 the complete entry of fixative will there- 

 by be prevented. After 3 or 4 hrs. the 

 specimen should be trimmed with a 

 new wet razor blade. 



Frozen sections are essential for rapid 

 diagnosis, for staining with Sudan and 

 for many other purposes. The tech- 

 nique most used by dermatologists is to 

 fix in Bouin's Fluid and to stain paraffin 

 sections with Hematoxylin and Eosin. 

 After Zenker Fixation, Mallory's Con- 

 nective Tissue Stain, or Masson's 

 Trichrome Stain, is suitable for muscle 

 and collagenic tissue. Weigert 's re- 

 eorcin fuchsin is recommended for elas- 

 tic fibers. The Dopa Reaction is re- 

 quired for melanin precursors. For 

 nerve fibers the Bodian method is prob- 

 ably the best. Another silver tech- 

 nique advised for the skin is that of 

 Jalowy. 



MacCardle, R. C, Engman, M. F., 

 Jr. and Sr., Arch. Dermat. & Syph., 

 1941, 44, 429-440 give details of spectro- 

 graphic analysis of skin lesions. See 

 also Microincineration. Ultracentrif- 

 ugation method for determination of 

 intranuclear viscosity (Cowdry, E. V. 

 and Paletta, F. X., Am. J. Path., 1941, 

 17, 335-357). Methods of transplanta- 

 tion are described by Kelly, R. W. and 

 Loeb, L., Anat. Rec, 1939, 74, 487-509 

 and of fluorescence examination by 

 Cornbleet, T. and Popper, H., Arch. 

 Dermat. and Syph., 1942, 46, 59-65. 

 An adaptation of the Sandison tech- 

 nique is recommended by Williams, R. 



