As meat and dairy products become scarcer and dearer we shall become increasingly dependent upon the vegetable fats. We should therefore devise means of saving what we now throw away, raise as much as we can under our own flag, keep open avenues for our foreign supply and encourage our cooks to make use of the new products invented by our chemists. CHAPTER XII FIGHTING WITH FUMES The Germans opened the war using projectiles seventeen inches in diameter. They closed it using projectiles one one-hundred millionth of an inch in diameter. And the latter were more effective than the former. As the dimensions were reduced from molar to molecular the battle became more intense. For when the Big Bertha had shot its bolt, that was the end of it. Whomever it hit was hurt, but after that the steel fragments of the shell lay on the ground harmless and inert. The men in the dugouts could hear the shells whistle overhead without alarm. But the poison gas could penetrate where the rifle ball could not. The malignant molecules seemed to search out their victims. They crept through the crevices of the subterranean shelters. They hunted for the pinholes in the face masks. They lay in wait for days in the trenches for the soldiers' return as a cat watches at the hole of a mouse. The cannon ball could be seen and heard. The poison gas was invisible and inaudible, and sometimes even the chemical sense which nature has given man for his protection, the sense of smell, failed to give warning of the approach of the foe.