SECTION 1. Article eighty-one of the Penal Code of the Philippine Islands is hereby amended to read as follows:
"ART. 81. In cases in which the penalties prescribed by law contain three degrees, whether it be a single divisible penalty or composed of three different penalties, each one of which forms a degree in accordance with the provisions of articles ninety-six and ninety-seven, the courts shall observe for the application of the penalty the following rules, according to whether there are or are not mitigating or aggravating circumstances:
"1. When there are neither aggravating nor mitigating circumstances, they shall impose in its medium degree the penalty prescribed by law.
"2. When only a mitigating circumstance is present in the commission of the act, they shall impose the penalty in its minimum degree.
"3. When only an aggravating circumstance is present in the commission of the act, they shall impose the penalty in its maximum degree.
"4. When both mitigating and aggravating circumstances are present, the court shall offset those of one class against the other according to their relative weight.
"5. When there are two or more mitigating circumstances and no aggravating circumstances, the court shall impose the penalty next lower to that prescribed by law, in the degree that it may deem applicable, according to the number and weight of such circumstances.
"6. Whatever may be the number and weight of the aggravating circumstances, the courts shall not impose a greater penalty than .that prescribed by law, in its maximum degree.
"7. Within the limits of each degree, the courts shall determine the extent of the penalty according to the number and weight of the aggravating and mitigating circumstances and the greater or lesser extent of the evil produced by the crime."