SEA-FISHERIES LABORATORY. 189 



SYLLABUS OF THE LESSONS GIVEN IN THE 

 CLASSES FOE FISHERMEN. 



Two lessons are given each day, each lesson lasting Jor 

 about two hours. 



First Day. 



The work of the first lesson is introductory, and will 

 deal with the use of the microscope and dissecting tools. 



Before going- on to the study of fishes and other 

 marine animals, it is necessary to learn something about 

 water and air, so as to understand the way in which 

 animals breathe. 



The Atmosphere.— Air consists chiefly of three gases, 

 nitrogen, oxygen and carbonic acid gas. In every 10,0U0 

 parts, by bulk, of air there are a little less than 2,100 

 parts of oxygen, about 7,900 parts of nitrogen, and about 

 four parts of carbonic acid gas. 



The oxygen of the air is necessary for the breathing 

 of animals and plants, and for combustion. Without it 

 animals or plants would not live, and fuel would not burn. 

 When an animal breathes, oxygen is taken into the body, 

 and combines with certain substances in the muscles and 

 elsewhere, producing mechanical energy and heat. When 

 a piece of charcoal or coke burns in the air, it combines 

 with oxygen. 



Nitrogen is not really necessary for breathing or for 

 combustion. It merely serves to dilute or weaken the 

 oxygen. 



Carbonic acid gas in the air comes principally from 

 the breathing of animals and from combustion of fuels. 



