This paper proves three statements of Schubert about cuspal cubic curves in a plane by using the concept of generic point of Van der Waerden and Weil and Ritt-Wu methods. They are relations of some special lines: 1) For a given point, all the curves containing this point are considered. For any such curve, there are five lines. Two of them are the tangent lines of the curve passing through the given point. The other three are the lines connecting the given point with the cusp, the inflexion point and the intersection point of the tangent line at the cusp and the inflexion line. 2) For a given point, the curves whose tangent line at the cusp passes through this point are considered. For any such curve, there are four lines. Three of them are the tangent lines passing through this point and the other is the line connect the given point and the inflexion point. 3) For a given point, the curves whose cusp, inflexion point and the given point are collinear are considered. For any such curve, there are five lines. Three of them are tangent lines passing through the given point. The other two are the lines connecting the given point with the cusp and the intersection point of the tangent line at the cusp and the inflexion line.

本文利用范德瓦尔登（Van der Waerden）和威尔（Weil）和里特-伍（Ritt-Wu）方法的类属点的概念，证明了舒伯特关于平面上的骨三次曲线的三个陈述。它们是一些特殊线的关系：1）对于给定点，将考虑包含该点的所有曲线。对于任何这样的曲线，有五条线。其中两条是通过给定点的曲线的切线。其他三个是连接给定点和尖点的线，拐点处的弯曲点和切线与拐点线的交点。2）对于给定的点，考虑其尖端处的切线穿过该点的曲线。对于任何这样的曲线，有四条线。其中三个是穿过该点的切线，另一个是连接给定点和拐点的线。3）对于给定的点，考虑其尖点，拐点和给定点共线的曲线。对于任何这样的曲线，有五条线。其中三个是穿过给定点的切线。另外两条是连接给定点和尖点的线以及在尖点和弯曲线的切线的交点。