CORRESPONDENCE 



303 



P.S. (July 28). — The experiments with Lemna plants at the 

 Imperial College of Science are proving the importance of 

 accessory food substances for plant nutrition. Plants growing 

 in Detmer's culture solution to which was added a small 

 quantity of the water-soluble organic substances from bacterised 

 peat have multiplied much more rapidly than those grown in 

 Detmer's solution alone. They have also increased in size 

 and retained their vigour, whilst the control plants have become 

 much smaller and are in a dying condition. The results after 

 five weeks' growth are : 



ANCIENT KNOWLEDGE OF PARASITE-CARRIERS 



From EM. PROF. H. A. STRONG, LL.D., Liverpool 



Sir, — May I venture to notice with reference to the most 

 interesting article J on the subject of the knowledge of the 

 ancients of animal and insect pests, and their influence on 

 health, that the Romans do not seem to have had any know- 

 ledge of the rat, and indeed possessed no word for that animal. 

 Even in Italy at the present day topo is used by most people 

 indifferently for a mouse or a rat. There seems no doubt, 

 as mentioned by Hehn {Kultarpflanzen und Hausthiere), that 

 at some early period after the great migration of the Aryan 

 tribes to the west, an immigration of rats occurred from Asia 

 (the Mus rattus). The various tribes composing the Aryan 

 people must have formed themselves into nationalities before 

 the advent of this animal, for we find that it bears different 

 names among the different Aryan nations. Thus the Polish 

 word for rat differs from the Russian, and the Slavs of the 

 Balkans have a different form again. The Irish called the 

 rat the Frankish mouse, and the modern Greeks still call it 

 the Pontic mouse : showing that they regarded it as coming 

 from the East. The Italian topo is simply a variant of talpa, 

 1 Science Progress, April 1916, by Joseph Offord. 



