Marvels of the Universe 



97 



Common as is the experience of being stung by this common hedgerow weed, few of its victims 

 trouble to inquire by what means so dehcate a contact can cause so much annoyance and irritation. 

 Yet the sting of the Nettle is worthy of a little examination, for though its mechanism is so simple 

 it is wonderfully efiS.cient. If, with an ordinary pocket-lens, we examine the leaf or stem of the 

 Nettle we shall discover that it is closely covered with very fine hairs. If we go further and submit 

 one of these hairs to the more powerful lens of a microscope so as to increase its apparent size fifty 

 times we shall see the hair as it is represented in our photograph. The hair, it will be seen, has a 

 bulbous base from which it tapers to a fine point, where, however, it bends and slightly swells into 

 a knob. In the enlargement this looks like a design to prevent the sting acting, and to be much like 

 the button on the point of a fencing-foil. But just below the little knob the hair is exceedingly 

 brittle, and the sHghtest touch will snap it across, leaving the now unprotected point free to enter 

 the skin. 



The hair, fine as it is, is pierced throughout its length by a tube which connects it with the swollen 

 base, which is really a bag fiUed with poison. The pressure necessary to drive the point through the 

 victim's skin also e.xerts itself upon the base, with the result that a minute drop of the poison is 

 forced through the hoUow hair into our blood, to be followed by the local irritation which sets up the 

 small white swelling around the puncture. The fineness of this hair is made readily apparent to the 

 eye by comparing it with an equal length of the point of the finest needle that is made, magnified 

 to precisely the same degree — fifty times its thickness. Beautifully polished as the needle is, the 

 microscope reveals a few burrs upon it, such as are not to be found on the Nettle's sting. 



J'lwlobu} [/', //. riihrf. 



IHE SCARAB'S HAK\ES1. 



The Sacred Beetle is a dung-feeder ; and here we have a party of Scarabs attracted to the feast, and busy rolling it into 



balls that they may push it away to the underground burrows they have prepared. 



