TECHNICAL NOTE.--Although this description is written for the toad it will fit for the dissection of the frog. It will be found, after casting aside a few ungrounded prejudices, that the toad is the better for class dissection. Toads are best collected about dusk, when they can be picked up in almost any garden in town or in the country. During the spring many can be found in the ponds where they are breeding. To kill the toad place it in an air-tight vessel with a piece of cotton or cloth saturated in chloroform or ether. When the toad is dead, wash off the specimen and put in a dissecting pan for study. Several specimens should be placed in a nitric acid solution for a day or so (for directions for preparing, see p. 12) to be used later for the study of the nervous system. Also several specimens should be injected for the better study of the circulatory system. With an injecting mass made as directed on p. 451 introduce through a small canula into the ventricle of the heart. This will inject the arterial system, and with increased pressure the injecting mass may be forced through the valves of the heart, thus passing into the auricles and throughout the venous system. After injecting use the specimen fresh or after it has been preserved in 4% formalin. =External structure.=--Note that the body of the toad is divided into several principal regions or parts, as is the human body, namely, a _head_, _upper limbs_, _trunk_, and _lower limbs_. As you look at the toad note the similarity of the parts on one side to those of the other, as right leg corresponding to left leg, right eye to left eye, etc. This arrangement of the body in similar halves among animals is known as _bilateral symmetry_. As a rule animals which show bilateral symmetry move in a definite direction. The part that moves forward is the _anterior end_, while the opposite extremity is the _posterior end_. In most animals we note two other views or aspects; that which is called the "back" and with most animals is, under ordinary conditions, uppermost is the _dorsum_ or _dorsal aspect_, while that which lies below is the _venter_ or _ventral aspect_. When referring to a view from one side we speak of it as a right or left _lateral aspect_. These terms hold good for most of the animals that we shall study.