RADIOAUTOGRAPHY 



153 



Geiger-Miiller counter or the electroscope. Radioautography, based 

 on the ability of emanations from radioactive elements to affect the 

 photographic plate, is an attempt toward the solution of this difficult 

 problem. Tissue sections containing radioactive elements leave their 

 "autographs" on photographic plates when placed in contact with 



Fig. 31. Emission electron micro- 

 graph (X300) showing calcium and 

 magnesium distribution in rectus ab- 

 dominus muscle of cat. Note strong 

 cross-bandings in muscle fibers. From 

 Scott (1943) 



Fig. 32. Emission electron micro- 

 graph of cat gastric mucosa (fundus) 

 showing calcium and magnesium dis- 

 tribution (left), compared with a 

 microincinerated section from the 

 same animal (right). Magnification 

 about X75. From Scott (1943) 



them for a sufficient period. When developed, these "autographs" 

 indicate to some degree the relative distribution of the substances 

 responsible for the radioactivity. 



Historically, the first use of radioautography was made by 

 Lacassagne and Lattes ( 1924) for the demonstration of polonium in 

 tissue. Since that time the usefulness of this technique, as well as all 

 others employing radioactive tracers, has been greatly expanded by 

 the recent revolutionary developments which have made possible 

 the preparation of radioactive isotopes of elements that occur in 

 living systems. Limiting factors in regard to the suitability of a 

 radioactive isotope for studies by radioautography are the nature 

 and intensity of its radiation and its half-life period. The duration 

 of the photographic exposure will depend on these factors as well as 

 on the concentration of the isotope in the tissue. The half-life 

 periods of the principal artificial radioactive elements that might be 

 used in tracer studies are given in Table V. 



Perhaps, the greatest deficiency of the technique of radioautogra- 



