X-RAY MICROSCOPY 



Fig. 11. MRD of a normal rabbit heart after 

 post mortem coloring with thorotrast, 25 m, ap- 

 prox. X35. 



Selective absorption of thorotrast by contract- 

 ing muscle substance is conspicuous. 



sion. Besides that, paraffin absorbs x-rays 

 and may produce erroneous images. 



Bohatirchuk (unpublished) has immersed 

 15 M (or thicker) frozen sections of cat spinal 

 cord for 24 hours into the following solu- 

 tions: thorotrast, neo-silvol (colloidal silver 

 iodide, 24% of silver), iodocol sol (iodine 

 8%), ferrocol sol (colloidal iron 3.5%), 

 sequestrol (colloidal lead, 6%) and Lange's 

 colloidal gold solution (0.01%). The most 

 conspicuous selective adsorption found in 

 microradiographs was that of thorotrast. All 

 other solutions were either adsorbed very 

 little (neo-silvol) or could not be detected in 

 microradiographs at all. Note, however, that 

 microradiography in this experiment was 

 done with 1.2 A (8 kv) x-rays; it is possible 

 that softer radiation would bring to view 

 also tissues only slightly colored with OM 

 (the description of morphological findings 

 will be given later). Apparently, silver is 

 selectively adsorbed by the same tissue ele- 

 ments as thorotrast. However, final conclu- 

 sions on the adsorption (or absorption) of 

 silver and other OM (with the exception of 

 thorotrast) depend on further study. 



Selective adsorption (or absorption) of 

 OM depends probably upon the signs of 

 electrical charges in both adsorbent (OM) 



and adsorber (element of biological tissue). 

 Adsorber and adsorbent must have opposite 

 charges in order to be attracted. This as- 

 sumption may be proved in the case of 

 thorotrast adsorption by positively charged 

 or amphoteric tissues. Fig. 11 shows a 

 macroradiograph of heart muscle of rabbit 

 after a section of it was immersed into 

 thorotrast for several hours. It is obvious 

 that the amphoteric contracting muscle 

 substance selectively adsorbs OM. Another 

 example is the adsorption of thorotrast by 

 positively charged collagen. It is known also 

 that thorotrast is never absorbed by nega- 

 tively charged tissues such as cartilage, 

 chromatin, etc. One should mention that 

 biological tissues do not show any affinity 

 for neutral OM (e.g., for barium and bismuth). 



All these data support the old Ehrlich 

 theory of coloring, according to which the 

 sign of electrical charge is primarily re- 

 sponsible for the adsorption (or absorption) 

 of dye (Baker) (5). 



Summarizing data on x-ray coloring in 

 general, we may say that this method can 

 be used in microradiography and should 

 bring, even with the limitations of magnifi- 

 cation mentioned above, new data impor- 

 tant for medico-biological research. 



Comparison of jVIicroradiographic Data 

 with those of Other Methods used in 

 Anatomy and Histology 



As was mentioned above, a microradio- 

 graph presents usually a real image of 

 a biological microstructure and not its 

 ''shadow" as many authors think (some of 

 them even use such a strange term as 

 "shadowgraph") (47). Only in an ordinary 

 photograph does one see sometimes an ob- 

 ject and its structureless shadow; in the 

 microradiograph each image is full of struc- 

 ture. In addition to that, it is possible to 

 color some microstructures, low in absorbing 

 x-rays, with OM and to study their real 

 image in microradiographs. The process of 

 selective absorption of OM and the follow- 



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