MICROSCOPICAL PURPOSES. 173 



inserting the tool between the bone and the covering of the brain, 

 (the Dura Mater) ; then pulHng away the piece of bone, we run no 

 risk of damaging the brain. 



After the bone has been removed from the top, spUt up the 

 Dura Mater, and with a pair of forceps pull out the bony septum 

 from between the cerebrum and cerebellum ; next, a little shaking 

 will show the nerve attachments, which hold the brain on its under 

 side. After these are cut the brain will fall out, and may be placed 

 in ordinary alcohol to harden. 



The spinal cord may be easily secured by using a wide chisel. 

 First place the trunk of the animal on its back, and with the chisel 

 cut the ribs from both sides of the vertebrae, letting the chisel 

 pass close to the vertebrae, and down through to the work-bench. 

 Next, let the slice containing the vertebrae lay on its side, set 

 the chisel on to the bone over the spinal cord, and with the ham- 

 mer tap on to the handle of the chisel, to make a longitudinal 

 fracture along the cord. Continue this the whole length of 

 the cord. 



Turn over the slice and repeat the fracture along the opposite 

 side ; then seize the two sides of the bone, one in each hand, and 

 pull them apart. The cord will then be set free with the nerve- 

 roots hanging to it. 



From various experiments respecting a connection between 

 thunderstorms and the souring of milk, Prof. H. \V. Conn draws 

 the conclusion that electricity is not of itself capable of souring 

 milk, or even of materially hastening the process ; nor can the 

 ozone developed during the thunderstorm be looked upon as of 

 any great importance. It seems probable that the connection 

 between the thunderstorm and the souring of milk is one of a 

 different character. Bacteria grow most rapidly in the warm, 

 sultry conditions which usually precede a thunderstorm, and it will 

 frequently happen that the thunderstorm and the souring occur 

 together, not because the thunder has hastened the souring, but 

 rather because the climatic conditions, which have brought the 

 storm, have, at the same time, been such as to cause unusually 

 rapid bacteria growth. 



