1894 THE MICROSCOPE. 93 



QUESTIONS ANSWERED. 



NOTB.— Z?r. S. G. Shanks, of Albany, N. Y., kindly consents to receive all sorts of ques- 

 tions relating to microscopy ,'whether asked by professionals or amat,ii> s ^f^'f^.^yy «^' 

 fades of experience, from the begi>nier upward, are welcome to the bentfts of this depar - 

 ment. The questions are numbered for future reference. 



V^l.— Wkai is a ''spot /e7is"?— S. 



Carpenter say a spot lens is a condenser with a permanent 

 axial stop fixed in it to cut off the central rays for the purpose 

 of obtaining a dark ground upon which the illuminated object 

 lies. Obviously it is not a desirable accessory. It is a con- 

 denser, but having a fixed stop it can only be used for this 

 mode of illuminatioQ. 



193. — Hoiv many &pedmen slides for the microscope icoidd he re- 

 quisite to a complete study of human anatomy f— Science Siftings. 



A complete series of mounts showing all the structures and ele- 

 ments of the body, would number many hundreds. A series of 

 about 100 preparations if well selected, would show all the typ- 

 ical and important tissues. Many of the sections would show 

 several sorts of tissues lor instance, transverse section of trachea 

 would show hyaline cartilage, involuntary muscle, mj^cous 

 glands, capillaries and ciliated epitheleum. A section of scalp 

 would show, epidermis and its epitheleum, hair root and 

 sheath, sebaceous and sweat glands, adipose, areolar and elastic 

 tissues. One section each, of kidney, liver, lung, ovary, testis, 

 etc., would show typical, structure and enable one to identify 

 the organ, but a complete demonstration of all the elements in- 

 volved, would require dozens of preparations for each organ. 

 About 300 varieties of elements and tissues are studied in a good 

 course in histology. 



PRACTICAL SUGGESTIONS. 



By L. A. WIIvLSON, 



CLEVELAND, OHIO. 



Foramenifera. — As we cannot conveniently take a stroll to 

 Iceland to collect specimens, we may do it indirectly by enter- 

 ing any drug store, and obtaining a little paper full of the sand 

 that comes in the packages with Iceland moss. This sand is 



