CHEMICAL SCIENCE. 178 



very similar to that of agriculture at the same period ; its resources 

 appeared to be in a state of exhaustion ; the rich capital of facts accu- 

 mulated in the department of organic morphology by the industry of 

 the anatomist, and by the acumen of the physiologist, could not yield 

 its full fruits until an equivalent of knowledge had been drawn from 

 the study of bio-chemical phenomena. This state of things, however, 

 is rapidly changing ; associated with chemistry, medicine no longer 

 draws the veil of vitality over processes, the mystery of which may be 

 unlocked by the key of analysis ; it no longer shrinks from climbing, 

 step by step, the ladder of recognition, because its upper extremity, 

 disappearing among the clouds, seems to rise forever beyond the grasp 

 of inquiry. The special zeal with which the field of organic chemis- 

 try has been cultivated during the last thirty years, the simple and 

 accurate methods which we now possess for determining the composi- 

 tion of organic products, the amount of analysis actually performed, 

 and, more than all, the still untiring energy oi' the numerous laborers 

 in the same field of investigation, hold out the promise that the con- 

 nection between medicine and chemistry, becoming daily more intimate, 

 will be productive of benefits, the importance of which we can scarcely 

 venture to estimate in the present state of our knowledge. 



NEW CHARACTEKISTIC OF THE SO-CALLED SEMI-METALS. 



The so-called semi-metals stand between the metals and metalloids, 

 marking the transition between these two classes of elements. They 

 share with the jirst, 1. The metallic lustre; 2. Conductivity of 

 heat ; 3. Conductivity for electricity ; 4. Density. 



With the metalloids they possess the property, 1. Of being acidifi- 

 able ; 2. Of forming only feeble salifiable bases ; 3. Of combining 

 easily with the metals in the manner of an electro-negative body ; 4. 

 Some of them form a gaseous compound with hydrogen. 



These characters are not absolute, and under them the semi-metals 

 may vary among themselves as much as they differ from other ele- 

 ments ; but notice a consideration which enables us to determine 

 nearly where the series of semi-metals begins and ends. 



The idea of malleability is the one which attaches itself most forcibly 

 to our notice of a metal. The word metal involuntarily recalls a body 

 sonorous, heavy, capable of being hammered and drawn into leaves 

 and wire or extended in the rolls. Viewed from this side, we find 

 certain of the metallic elements which possess neither malleability nor 

 ductility, and, strangely enough, these elements are those which we 

 know as acidifiable metals. Among them we find tellurium, tungsten, 

 osmium, arsenic, antimony, and lastly bismuth, which only lately passed 

 among the metals, but which has lately fallen from that rank, since 

 the establishment of its isomorphism with antimony and arsenic 

 themselves isomorphous with phosphorus and nitrogen. 



Bismuth has, in fact, all the external characters of the metals, 

 saving in its want of tenacity and its brittleness, peculiarities common 

 to all the other elements of a metallic lustre, which we call semi- 

 metals. 



Wanting tenacity, these elements ought consequently to possess 



15* 



