SCIENTIFIC DETECTION OF CRIME — SANNIE 353 



people. Expert examination showed that all these notes looked the 

 same, having the same miusual patches of fluorescence and similar rust 

 stains. Moreover, examination of their microscopic flora showed that 

 the same bacteria and fungoid growths were present on all of them ; in 

 particular, all were considerably affected by a rare and highly in- 

 dividual fungus, Acrostalagrrms cinnabarinus corda. The flora on 

 other notes kept in bundles or put into circulation was quite different. 

 It was thus possible to prove the common origin of the notes and to 

 confirm the complicity of the receivers. 



The advances of science do not always, however, make the expert's 

 task easier. Sometimes they make it much more complicated. We 

 may have a police laboratory which is perfectly familiar with the 

 methods of studying the usual textiles. Its members may be expert 

 in comparing the fibers of wool, cotton, silk, jute, hemp, linen, etc. 

 But the introduction of many synthetic textile fibers, to which the 

 familiar teclmiques can no longer be applied, raises new problems 

 which are sometimes extremely difficult to solve. The same is true of 

 artificial dyestuffs, the number of which is increasing daily, and of 

 the countless pharmaceutical products, some of which are dangerous 

 narcotics, capable of being used instead of the derivatives of opium or 

 coca. Their identification involves knowledge not only of their for- 

 mula and chemical properties but also of the methods of organic chem- 

 istry by which their chemical functions can be determined and 

 identified. 



One of the most striking features of this development in methods 

 is the substitution, for visual examination, of more complicated but 

 also more efficient techniques. For a long time, materials, textiles, 

 fibers, threads, animal and vegetable remains and dust were examined 

 by means of the magnifying glass and the microscope. But such visual 

 examination, and the interpretation of what is seen, necessarily depend 

 on the observer. Wlienever it is possible to use a physical or chemical 

 method instead of, or to supplement, visual observation, greater pre- 

 cision and certainty are ensured. Mineral dust, earth, and mud can 

 be identified under the microscope; and the use of a polarizing micro- 

 scope is in itself a great step forward. Lastly, the methods of mineral- 

 ogical analysis — separation by increasing densities, thermal analysis 

 by the methods of Saladin and Le Chatelier, or even the determination 

 of the magnetic moment — are still more efficient. More recently, X-ray 

 spectrography, by which crystalline structure can be determined, and 

 the electronic microscope with very high resolving power have been 

 used with great success in the identification of dusts. 



In the past, the only means of studying bones was by histological 

 examination, which revealed changes attributable to fossilization. 

 Fossilization can be followed still more accurately by means of chem- 

 ical analysis and, more particularly, by the quantity of fluorine wliich, 



